The Twin, Glacial lake in Rila Mountains, Bulgaria.

The Twin is a glacial lake in the Rila Mountains made up of two connected water bodies positioned at roughly 2,240 meters (7,350 feet) elevation. It forms part of a larger chain of seven lakes at different heights within the same mountain range.

The lake was formed during the last ice age when glaciers carved into the mountain rocks and left behind depressions that filled with water. The two basins visible today showcase the lasting impact of these ancient glacial processes on the landscape.

The name Bliznaka means "the twin" in Bulgarian, referring to the two basins joined by a narrow, shallow channel; the earlier Turkish name was Chifte göl, also meaning twin lake. The southern basin, ringed by steep rock walls where snowbanks linger into late summer, receives the outflow of the highest lake, Sylzata, while the shallower northern basin, edged with juniper, takes the water of the second and third lakes.

You can reach this lake by following marked hiking trails from the chairlift station at the base. The summer months from June through September offer the best conditions for the trek, as snow clears and paths are easier to navigate.

Its Turkish name, Chifte göl, also meant "double lake", a reminder of the Ottoman-era naming layer in the Rila Mountains. The southern basin is the deeper one, walled by steep rock where large snowdrifts linger into late summer, while the northern basin is shallow with juniper on its slopes.