Trekanten is the small lake at the heart of Liljeholmen, with a 2.5 km path around the water and a popular summer swimming beach. It is an easy local escape from central Stockholm, close enough for a relaxed walk but green enough to feel outside the city grid.
In warm weather people come for swimming, fishing, and ice cream by the water. In winter the same loop is good for a quiet walk, and when the ice is safe locals skate on the lake.