LUMMELUNDA CAVE also known as the ROBBERS’ DEN is located in a nature reserve at Lummelunda, north of Visby on Gotland, Sweden. The explored part of this “krast” cave is almost 4.5km, making it one of the longest caves in Sweden. It is created by the drainage water from the MARTEBO mire. The water forms a stream with its outlet in the Baltic Sea. In the 15th to the 19th centuries, mills and ironwork were set up near the stream.
Although the entrance of the cave has been known for centuries, the main part of it was discovered by three teenage boys during the 1940s and 1950s. It is visited by around 100,000 people every year and is one of the major tourist attractions on Gotland.
The cave was most likely formed before the last Ice Age. The water that creates it runs as a stream, the LUMMELUNDSAN, through the north part of the cave system exiting the limestone cliffs (known as the KLINT) a few 100 metres from the coastline. The stream was much larger and more forceful before the mire, once the largest on Gotland, was drained at the end of the 19th century. The remaining drainage is led through an underground 3,770ft canal, dropping 56ft from Martebo mire to LUMMELUNDA, at 400 litres/sec.
The stream has been used for industry since the Middle Ages. According to an undocumented litigation in 1778, a mill was built at Lummelunda in 1418. The oldest reliable record is from 1594, where 3 mills are listed at the stream. In the 1620s, 6 mills were in use at the Lummelundsan. The cave has been known as long as the stream has been used.
Carl Linnaeus wrote about the cave during his journey to Gotland in the summer of 1741. The part of the cave where the stream has its outlet, the LINNE’S CAVE, is named after him. The Linne’s Cave is 20ft wide, 9.8ft high and about 39ft long. The bottom of it is filled with water. The Lummelunda Cave is mentioned in the 1917 cave investigation made by geologist and a Gotlander Henrik Munthe, where it is called KYTT–JANNS KALLARE (Kytt-Jann’s cellar). The first documented attempt to explore was made in 1924, by zoologist Torsten Gislen, but he never got further than 130ft into the cave despite several later attempts. —– The breakthrough in finding the cave system happened in 1948, when 3 teenage boys ——– Lars Olsson, Orjan Hakansson and Percy Nilsson, known as THE THREE BOYS (De tre pojkarna) found an entrance to the rest of the cave. For 7yrs they explored the cave on Sundays using matches, candles, planks and a small boat to get deeper into the system. —-After having explored the first hall of the cave for 2yrs, a large block of stone fell from one of the walls widening a small opening in the cliff. This led to a 66ft long passage (later called THE BOYS’ PASSAGE —- Pojkarnas gang) into the first large cave hall, THE MOUNTAIN KING’S HALL —- (Bergakungens sal). From 1959 onwards, this hall became the location for the start of the “guided tours”. A bit further in is THE CHAPEL (Kapellet), named thus by the boys who thought it looked like a church, where their exploration was hindered by a lake.
It was not until 1955, that they managed to get another 574ft further in, using an inflatable boat. In 1959, a 200ft long tunnel was made from the surface to THE MOUNTAIN KING’S HALL, to make the cave more accessible to visitors. Another 1,300ft of tunnels and the largest hall so far was discovered by “cave divers” in September 1985, after they had passed 4 “underwater passages” or “traps”.
33 sinkholes have been found in the main canal leading the water from Martebo mire to the cave. In the area west of the cliff there are 5 springs. After the drainage of the mire, the flow of the water in the canal has decreased significantly from 190cu.ft/s in 1948 to 49cu.ft/s in 1977. This has caused some of the sinkholes to disappear. During dry summers, there is an impending danger that the cave will be completely drained.
The cave is roughly divided into 2 parts : one “dry” also called “fossil system”, and a “wet” —– “active part”. A large number of fossils and stalactite formations can be found in the “dry” part. The cave has a relatively stable climate with a humidity of 95-100%. According to a source from 1989, the temperature is on average 7degreeC, and points out that fluctuations in temperature have been noticed as a result of the many visitors. A source from 2011, states that the temperature is 8-12degreesC.
A nature reserve, to protect the Lummelunda Cave, was established on 20th March, 1989. The reserve is 42acres, it includes the cave and the corresponding area above the ground and is called the Lummelunda Cave Nature Reserve. At least 83 different species of animals including worms, spiders, centipedes, crayfish, beetles, butterflies, fish, bats and mice have been found in the cave. Plants grow near the artificial lights in the outer parts of the cave. Since the plants are not a natural part of it, they are removed to keep the environment as original as possible. The many visitors also have a negative effect on the biology of the cave. The landscape above the cave, which is also a part of the nature reserve, is characterized by the KRASTIFICATION of the area. It is bisected by a steep cliff running in a north-south direction through the reserve. The eastern part on top of the cliff is covered in “pine” forest and the western part, between the cliff and the shore, is grassland with “deciduous” trees.
The Lummelunda Cave has been open to the public since 1959. THE MOUNTAIN KING’S HALL and THE CHAPEL (these combined are called the VISITORS’ CAVE) are included in the regular tours. It is also possible to go another 1,600ft into the cave system with the special tours. These tours require a trained guide and visitors have to wear special gear and use small boats.
On 21st January, 2011, THE THREE BOYS were honoured in a ceremony at the Campus Gotland. One of the boys (Percy Nilsson died in December 2013. All the three boys were made Honorary Members of the Swedish Society.