The impressive sinkhole near Hranice town – Hranice Abyss – has been known for centuries. But over the last decade it turns out that this is a landmark of world importance – the small lake at its base is the deepest cave lake in the world!


The sinkhole is located in nature reserve "Hůrka u Hranic" and is accessible by a marked trail.

This giant abyss is visually very impressive and might be dangerous if the visitor steps too far. The hole is 104 by 34 m wide and its depth until the lake is 69.5 m deep. This upper part of the cave is collapsed cave room.

Lake at the base of the sinkhole (named Jezírko) does not look like something special. This small waterbody is covered with fallen leaves, branches, and other debris. Nevertheless, it is unique – it is incredibly deep!

On the 27th September 2016 this lake was dived up to the depth of 404 m thus turning it into the deepest known cave lake in the world. But this is not all: basing on the measurements of temperature and chemical composition the total depth of this cave is between 800 – 1200 m!

The cave lake consists of several enormous, vertical chambers which are connected by narrow passages.

Jezírko - bottomless lake in Hranice Abyss, Czechia
Jezírko – bottomless lake in Hranice Abyss / Jiří Komárek, Wikimedia Commons / CC BY-SA 4.0


The area around Hranice town has many interesting karst formations – caves and quite many sinkholes. In the Devonian limestone have developed beautiful landmarks, such as Zbrašovské aragonite caves.

Hranice Abyss though is a very special landmark. The upper rim of this cave is located 315 m above the sea level, which means that the cave goes deep under the sea level.

This abyss has not been formed by the common karst processes, where the limestone is dissolved by groundwater which flows down through the fissures. Here, in Hranice Abyss the cave is dissolved by thermal water and carbon dioxide bubbles in it. These bubbles rise upwards, like in champagne. This carbonated water comes up from great depth, on its way dissolving large voids in the limestone. This is thermal water with a temperature of 16.5 °C.

The carbonated water is felt also by the divers – it makes the skin itch.


The giant pit at Bečva River has been known for a long time. This is the deepest abyss in Czechia.

According to local legends here with his horse jumped ruler of Great Moravia Mojmír II (or Mojmír I). In the same night, his entourage followed him in the abyss.

Since the medieval times people have tried to measure the depth of the lake in the abyss. Step by step researchers dived deeper and deeper. In 1968 was reached the depth of 88 m, in 1980 – 260 m. Due to complex passages further dive required development of new technologies – small robotic submarines.

Diverse submarines were tested here since the 1980ies and over the last decade most successful have been Polish made (GRALmarine) robots. Such dives are extremely complex and require much skill and luck.

World’s deepest cave dive was made here on the 27th September 2016 by a joint Polish-Czech expedition which was led by Polish diver Krzysztof Starnawski. They managed to reach the depth of 404 m, divers themselves reached the depth of some 200 m. The robotic device could not go further down as the cable for it was too short.

Thus by 12 meters was exceeded the previous cave dive record – 392 m in Pozzo del Merro, Italy, which was reached in 2002.


  1. National Geographic. Exclusive: Deepest Underwater Cave Discovered. Accessed on October 1, 2016
  2. ZO ČSS 7-02 Hranický kras. Accessed on October 1, 2016
Hranice Abyss on the map
Travelers' Map is loading...
If you see this after your page is loaded completely, leafletJS files are missing.
Location, GPS coordinates: 49.5322 N 17.7507 E
Categories: Sinkholes, Caves, Lakes and streams, Geographical extremes
Values: Geology, Visual, Biology
Rating: 3
Where is located? Europe, Czechia, Olomouc Region, south from Hranice town, at Teplice nad Bečvou village, on the upper rim of the right, eastern bank of Bečva River
Name in Czech: Hranická propast
Depth: known – 473.5 m, waterbody – 404 m
Depth of sinkhole: More than 100 m

Landmarks of the Czechia

Centre of Prague, Czechia
Centre of Prague / G.Pāvils, CC-BY-SA-3.0

The heritage of Czechia is very diverse and especially rich and diverse is man made heritage – from archaeological landmarks to the achievements of modern architecture. Among the numerous amazing landmarks the most interesting here are historical cities and towns, castles and churches.


Entrance into Puerto Princesa Subterranean River, Philippines
Entrance into Puerto Princesa Subterranean River / , Flickr / CC BY 2.0
Every year there are reported exciting discoveries of new caves and discoveries of new qualities such as cave paintings in the ones known before. But there still is a feeling that our knowledge covers just a small part of all these monuments of nature.

Though, those which are known to us offer a surprising diversity of unusual features and impressive sights.

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