Opal Lake is a dramatic and unique lake located at Hammerknuden in northern Bornholm. The lake is the water-filled pit of a former granite quarry — from the late 19th century until 1971, the area was part of Bornholm’s significant granite industry, with the stone exported from the nearby harbour.
After quarrying ceased, the pit slowly filled with water, and today it forms a deep lake surrounded by steep rock walls. Opal Lake attracts many visitors due to its combination of natural beauty, history and activities: During summer, it is possible to jump into the water from the cliffs, use a zipline across the lake, or hike along trails that wind through the rugged landscape.
In addition, Opal Lake forms part of the large Hammerknuden nature area, where — besides the lake — visitors can experience rocky coastline, rock formations and access to trails that connect to other natural and cultural-historical sites in the area.
