Stalactites and stalagmites: what they are, how a cave forms and where to see them in Romania
A stalactite hangs from the cave ceiling, a stalagmite grows up from the floor towards it. To remember which is which: stalacTites have a T for top, stalaGmites have a G for ground. Both are made of calcite, the mineral limestone is made of, and both grow from the same drop of water: part of the calcite stays on the ceiling, the rest falls to the floor. They grow very slowly, usually less than 10 cm in 1,000 years, and when they join they form a column.
Below, in order: what a cave is and what karst means, how a cave forms, how stalactites grow and why you must not touch them, the other formations (draperies, gours, cave pearls, crystals), why a cave is just as cold in summer as in winter, what lives there and which caves in Romania show them best. All the caves you can visit, by region, are in the guide to caves in Romania.
In short
- Stalactites hang from the cave ceiling and stalagmites grow up from the floor beneath them; when the two join, they form a column.
- Stalactites and stalagmites form from water loaded with dissolved limestone: in the cave air the water loses carbon dioxide and leaves calcite behind.
- A limestone stalactite usually grows less than 10 cm in 1,000 years, and a stalagmite at roughly the same rate; thin, hollow tubes grow faster.
- Karst is the landscape formed when water dissolves limestone (and gypsum or salt): caves, shafts, sinkholes, karst springs.
- The temperature in a cave stays almost the same all year, close to the local annual average: 8–12 °C in most of Romania's show caves.
- Touching stalactites is forbidden in Romania's caves because the grease on your hands leaves marks and changes how water runs over the formation, and a broken stalactite will not grow back within a human lifetime.
- Stalactites, stalagmites, columns and draperies are easy to see in the show caves Urșilor, Muierilor, Polovragi, Meziad and Valea Cetății.
Stalactites, stalagmites and other cave formations at a glance
All cave formations go by one scientific name: speleothems. Most are made of calcite and are born from water that drips, flows or stands still. The table shows how each one forms, how fast it grows, where a figure exists, and in which cave on the site you can see it.
| Formation | How it forms | How fast it grows | Where to see it on the site |
|---|---|---|---|
| Stalactite | hangs from the ceiling; each drop leaves a ring of calcite at its edge | usually under 10 cm in 1,000 years; thin tubes grow faster | Bears' Cave (Gallery of Candles, Spaghetti Hall), Women's Cave |
| Stalagmite | grows up from the floor where the drop lands; usually thicker than the stalactite above it | at about the same rate as a stalactite | Valea Cetății Cave (one about 2 m tall), Polovragi Cave |
| Column | a stalactite and a stalagmite that have joined | tens of thousands of years or more; no general figure is published | Ialomița Cave ("La Altar"), Românești Cave (7 m), Women's Cave |
| Drapery | water runs down a sloping ceiling and leaves a thin strip of calcite, like a curtain | no general figure is published | Meziad Cave, Bears' Cave, Comarnic Cave |
| Gours (calcite pools) | calcite rims that grow around pools, in steps | no general figure is published | Comarnic Cave, Ialomița Cave (Decebal's Vault) |
| Cave pearls | beads of calcite grown layer by layer around a grain of sand, in small pools | a nest in Piatra Altarului was dated to about 14,000 years | Românești Cave |
| Helictites | formations twisting in any direction, fed by water rising through a tiny inner channel | no general figure is published | no cave on the site mentions them |
| Calcite crystals | grow on the walls of closed cavities with no link to the outside | no general figure is published | Crystal Cave of the Farcu Mine |
| Ice stalagmites | water dripping from the ceiling freezes on the floor | grow every spring and partly melt in summer | Scărișoara Ice Cave (the Church area) |
Growth rates: Science Focus (BBC) and the National Park Service (pages on speleothems); the Piatra Altarului pearls, stalagmites and columns: the cave pages on the site, checked on 31 October 2026. "No general figure is published": the rate depends on how much calcite the water carries and how often it drips.
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What is a cave and what is karst
A cave is a natural hollow underground, big enough for a person to enter. Most caves in the world, and almost all of those in Romania, are carved into limestone, a rock that water can dissolve.
Rainwater is not quite pure. As it passes through the air and above all through the soil, where plants and their rotting remains produce a lot of carbon dioxide, it takes some up and becomes a weak acid, carbonic acid, the same that makes the bubbles in sparkling water. This acid slowly dissolves the calcite in limestone and carries it away, like sugar dissolved in tea.
Karst (from the German Karst) is, according to the Romanian dictionary DEX, the dissolving of limestone, gypsum and salt by water, and also the landscape that results: caves, shafts (round chasms in limestone into which water drains, called aven in Romanian), sinkholes, gorges, rivers that vanish underground and come back up through karst springs. In Romania, karst landscape is typical of the Apuseni Mountains, Banat, sub-Carpathian Oltenia and the Bucegi. Cetățile Ponorului, in the Apuseni, gathers almost all of its forms in one place.
Top 100How a cave forms: the stages
- Water enters the cracks. Acidic water seeps through cracks in the limestone and widens them little by little. Where the rock is heavily cracked, the dissolving spreads out and no cave forms; where the water follows a few large cracks, it concentrates on them.
- The passage widens under water. Caves usually form while filled with water, below the water table. Along the main paths, the flow keeps widening the passages.
- The cave drains. A nearby river deepens its valley, the water level drops and the upper passages fill with air. That is how caves on several levels come about: Comarnic Cave has three, one where water flows all the time, one flooded only by spates and one dry, fossil level, the only one open to visitors. Women's Cave has four levels.
- The cave is decorated. Only in air-filled passages can dripping water leave calcite behind: stalactites and stalagmites appear. Active caves, with a stream still running through them, like Bolii Cave, impress more by their size and their water than by their stalactites.
Time is measured on a geological scale. At Movile Cave, near Mangalia, the hollows began to form about 5.5 million years ago and are still forming today, but there the limestone is dissolved by sulphuric acid from thermal water, not by carbonic acid.
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How stalactites and stalagmites grow and how much they grow a year
Water that has dissolved limestone above the cave reaches its ceiling through cracks. The cave air holds less carbon dioxide than the water in the soil, so the drop loses some of it. Without that carbon dioxide, the water can no longer hold all its dissolved calcite and leaves it behind as a thin ring at the edge of the drop. Drop after drop, the ring becomes a hollow tube known as a soda straw. In Bears' Cave you see them in the Gallery of Candles and the Spaghetti Hall, and in Românești Cave they are called "macaroni". When the tube clogs, water runs down the outside and the stalactite thickens.
The drop that falls to the floor still holds a little calcite, which it leaves where it lands: that is how a stalagmite grows, usually thicker and more rounded than the stalactite above it. How much it grows a year depends on how much calcite the water carries and how often it drips. Limestone stalactites usually grow less than 10 cm in 1,000 years, that is under a tenth of a millimetre a year, and stalagmites at about the same rate. Thin tubes grow faster, because all the calcite gathers on a narrow ring. Stalactites under concrete bridges grow much faster, up to a centimetre a year, but concrete is not limestone.
Because they form layer by layer, a stalagmite can be dated like the rings of a tree. In Vârtop Cave, a stalagmite that grew over a Neanderthal footprint was dated to about 62,000 years, so the footprint is older still.
Why you must not touch stalactites
The rules of Romania's show caves say it plainly: at Bears' Cave, Polovragi Cave, Women's Cave or Ialomița Cave you do not touch or break the formations. There are three reasons.
- The grease on your hands. When you touch a formation, you leave grease, skin cells and lint on it. This layer changes how water spreads over the calcite and can stop growth at that spot; over time it also turns dark.
- Time. At under 10 cm in 1,000 years, a one-metre stalactite needs more than ten thousand years to grow. A broken one will not grow back within a human lifetime.
- The cave is fragile. Researchers at the "Emil Racoviță" Institute of Speleology (Institutul de Speologie „Emil Racoviță”) warned, when they began monitoring five show caves (Urșilor, Meziad, Muierilor, Polovragi and Valea Cetății), that improper use can damage a cave irreversibly in a very short time. Carbon dioxide, dust carried by air currents and the light of the lamps, around which algae and mosses grow ("lamp flora"), change the environment.
Dâmbovicioara Cave shows the result: for a long time it was visited with torches and candles, without any protection, and many of its formations have been lost.
Columns, draperies, gours, cave pearls and crystals
A column appears when a stalactite and the stalagmite below it meet. In Women's Cave you can see a stalactite that almost touches the tip of a stalagmite, a column in the making; in Ialomița Cave, the spot called "La Altar" is formed by two calcite columns.
Draperies grow where water runs down a sloping ceiling and leaves a thin trail, which over time becomes a wavy curtain. You see them in Meziad Cave, in the wide passages of the lower level, and in Comarnic Cave. When water flows over walls or floor, it leaves flowstone, like a frozen waterfall.
Gours are small stepped calcite pools, grown at the edge of puddles. Comarnic Cave has large gours, some full of water, and in Ialomița Cave they cover the bed of the underground stream in Decebal's Vault.
Cave pearls form in small pools where water drips: a grain of sand rolls about and is coated, layer by layer, in calcite. Helictites grow crooked, in any direction, because water feeds them through a tiny inner channel, not by dripping.
Calcite crystals grow large when the cavity has no link to the outside. The Crystal Cave of the Farcu Mine, in the Pădurea Craiului Mountains, was opened by miners and has its walls covered in crystals; the red or ochre colours in other caves, as at Muierilor, come from iron oxides in the water.
Top 100Why caves have the same temperature all year round
The thick rock above insulates the cave from summer heat and winter frost. That is why the average temperature in a cave is close to the annual average of the surface air at the same place, and the differences between seasons are much smaller than outside: a study of caves in several climate zones measured annual ranges of 0.1 to 8.8 °C in caves, against up to 32.2 °C at the surface.
Most of Romania's show caves are at 8–12 °C all year: 8–9 °C in Polovragi Cave, about 10 °C in Bears' Cave and at Muierilor, 9–12 °C at Meziad and in Valea Cetății Cave. Higher up it is colder: Ialomița Cave, at 1,660 m in the Bucegi, has 5–6 °C. The exceptions come from ice or warm water: the Scărișoara Ice Cave is around 0 °C in summer, while Movile Cave has 21 °C because of its thermal water. What to wear and which shoes to bring is in the practical section of the caves guide.
What lives in caves: bats and eyeless animals
There is no light in a cave, so no plants grow; food comes from outside, with the water, with animals that go in and out or from bat guano. Biologists sort cave animals into three groups:
- guests, which go in and out, like bats: they roost or hibernate in the cave and hunt outside. At Polovragi Cave about 300 horseshoe bats spend the winter, and at Meziad, in the Bats' Hall, one of the largest colonies in the country. That is why some caves close in winter, so that hibernating bats are not woken;
- cave lovers, which can live both inside and outside (some spiders and beetles);
- true cave dwellers, which spend their whole lives in the dark. Many are white or pinkish, without pigment, with small eyes or none and long legs and antennae, which they use to feel their way.
The most unusual ecosystem is in Movile Cave, sealed off from the surface: there, food is produced by bacteria that live on sulphur and methane, and 37 species of invertebrates are found nowhere else. The cave cannot be visited; why, and what you can see instead, is in the guide to caves you cannot visit. Caves have also kept traces of people: the charcoal drawings in Coliboaia Cave, about 32,000–36,000 years old.
Ice in caves and the records
In some caves it is so cold that dripping water freezes: that is how ice stalactites and ice stalagmites appear, as in the Church area of the Scărișoara Ice Cave, where they grow every spring from meltwater. Romania's underground glaciers are in the guide to ice caves.
Which is the longest, the deepest or the largest cave in the country is in the guide to the records.
Top 100Caves with stalactites and stalagmites in Romania: where to see them best
Formations are easiest to see in show caves, with lighting and walkways:
- Bears' Cave, at Chișcău (Bihor): candle-thin stalactites, columns and draperies, plus the bones of cave bears; the most visited cave in Romania.
- Women's Cave, at Baia de Fier (Gorj): stalactites, stalagmites and columns, white or stained with ochre, along 860 m of passage.
- Polovragi Cave, in the Olteț Gorge (Gorj): in the Ogive Sector there are stalactites, columns, domes, groups of stalagmites and pools of water.
- Meziad Cave, in the Pădurea Craiului Mountains (Bihor): stalactites, stalagmites, columns and draperies in halls 15–20 m high.
- Valea Cetății Cave, near Râșnov (Brașov): flowstone on the walls and a stalagmite about 2 m tall.
- Vadu Crișului Cave, in the Crișul Repede Gorge: stalactites, stalagmites and columns along a 680 m route.
For a cave without electric light, with gours and draperies seen by headlamp, Comarnic Cave, in the Anina Mountains, is visited with the park rangers between April and October. Opening hours, prices and directions are on each cave's page.
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Common mix-ups: stalactite or stalagmite, cave, grotto or shaft
- Stalactite or stalagmite? The one on top, on the ceiling, is the stalactite (T for top); the one below, growing from the floor, is the stalagmite (G for ground). A column is both, joined.
- Cave or grotto? In Romanian, the DEX gives grotă as a literary synonym for cave, borrowed from French. In the names of chambers inside a cave, a grotto is usually one part, like Mihnea Vodă's Grotto at the entrance to Ialomița Cave.
- Cave or shaft? A shaft (aven) is a vertical pit in limestone, open at the surface, through which water drains. At Scărișoara you go down a 60 m wide shaft to reach the cave entrance.
- Salt caves. Salt dissolves in water too, so there are also hollows in salt massifs, but the salt mines visited by tourists were dug by people, they are not natural caves. They are in the guide to salt mines in Romania.
- Calcite or ice? The ice stalactites at the entrance to Ialomița Cave in hard winters melt in spring; calcite ones last thousands of years.
Frequently asked questions
- What is the difference between stalactites and stalagmites?
- Stalactites hang from the cave ceiling and stalagmites grow up from the floor beneath them. To remember: stalacTites have a T for top, stalaGmites have a G for ground. When they join, they form a column.
- What are stalactites and stalagmites?
- They are calcite formations in caves, left by dripping water. The water dissolves limestone above the cave, then in the cave air it loses carbon dioxide and deposits calcite on the ceiling (stalactite) and on the floor (stalagmite).
- How fast does a stalactite grow per year?
- Usually less than a tenth of a millimetre: limestone stalactites grow less than 10 cm in 1,000 years. Thin, hollow tubes grow faster, and the rate depends on how much calcite the water carries and how often it drips.
- Why should you not touch stalactites?
- The grease on your hands stays on the calcite, can stop growth at that spot and darkens the formation. A broken stalactite needs thousands of years to grow again, which is why show-cave rules forbid touching and breaking formations.
- What is karst?
- Karst is the dissolving of limestone, gypsum and salt by water and the landscape that results: caves, shafts, sinkholes, gorges and karst springs. In Romania it is typical of the Apuseni, Banat, sub-Carpathian Oltenia and the Bucegi.
- What is a cave?
- A cave is a natural hollow underground, big enough for a person to enter. Most are carved into limestone by rainwater, which picks up carbon dioxide in the soil and becomes a weak acid.
- How is a cave formed?
- Acidic water widens the cracks in limestone, the passages grow while they are full of water, then the water level drops and the cave fills with air. Only then do stalactites and stalagmites appear. It takes a very long time: at Movile Cave, the hollows began to form about 5.5 million years ago.
- What is the temperature inside a cave?
- Almost the same all year, close to the local annual average: 8–12 °C in most of Romania's show caves. Ialomița Cave, at 1,660 m, has 5–6 °C, and the Scărișoara Ice Cave is around 0 °C in summer.
- Why do plants not grow in caves?
- Because there is no light, which plants need to make their food. In caves, food comes from outside, with water and animals, and in Movile Cave it is produced by bacteria that live on sulphur and methane.
- Where can you see stalactites and stalagmites in Romania?
- In lit show caves such as Bears' Cave (Bihor), Women's Cave and Polovragi Cave (Gorj), Meziad Cave (Bihor) and Valea Cetății Cave (Brașov).
Sources
- National Park Service: Speleothems (cave formations): stalactite, stalagmite, column, drapery, cave pearls, helictites
- National Park Service, Ozark National Scenic Riverways: How stalactites and stalagmites form (carbonic acid, the "T for top, G for ground" rule)
- National Park Service, Great Basin: Speleothems (thin tubes grow faster; rimstone, helictites)
- National Park Service: Learn About Caves, lesson plan (visitor impact, skin oils)
- National Park Service, Ozark National Scenic Riverways: The Biology of Caves (trogloxenes, troglophiles, troglobites)
- U.S. Geological Survey: Karst aquifers (karst, caves, springs)
- Penn State University, GEOSC 10: Forming caves, cave formations, and their surroundings (the stages of cave formation)
- Science Focus (BBC): How long does it take stalagmites and stalactites to form? (under 10 cm in 1,000 years)
- Medina et al., Scientific Reports 13:20735 (2023): Temperature variation in caves and its significance for subterranean ecosystems
- Alba24: the "Emil Racoviță" Institute of Speleology project to monitor show caves (20 September 2014, in Romanian)
- DEX online (Romanian dictionary): carst (karst)
- DEX online (Romanian dictionary): avenă (shaft)
- DEX online (Romanian dictionary): grotă (grotto)
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