Lake Voulismeni (Gr: Λίμνη Βουλισμένη) or just "the Lake" for the locals, is located at the centre of the town of Agios Nikolaos. It has a circular shape of a diameter of 137 m and depth 64 m. The lake connects to the harbour of the town by a channel dug in 1870.
A panoramic view of the lake can be seen from a small park situated above it. According to legend, the goddess Athena bathed in it. Every year at midnight turning to Orthodox Christian Easter day, the majority of the population of the town gathers around the lake to celebrate with fireworks, and firecrackers.
It was reported that the German army during their withdrawal from the area at WW2, disposed parts of their weaponry and/or vehicles into the deep lake.
A local urban legend has it that the lake is bottomless. That notion is potentially based on its impressively disproportional high depth compared to its width (64m depth on only 134m width) or/and on locals noticing disturbances at the surface or also the level of the water during the Santorini (Thera) earthquake of 1956. Because of the latter, many assume a possible geological relation of the two locations, but this claim has not been substantiated by known scientific surveys to date.