Lake Vouliagmeni

The lake formed when the roof of a large underground cavern collapsed, leaving a pool at the foot of a limestone cliff, connected to the sea by an underwater channel and fed by warm mineral springs from deep in Hymettus. The mix keeps the water between about twenty-two and twenty-nine degrees Celsius all year, so people swim here in January, and gives it a brackish, mineral-rich composition long credited with easing skin and joint complaints. Small fish that clean bathers' feet live along the shallows. Divers have mapped a flooded cave system extending hundreds of metres under the cliff, one of the more demanding cave dives in Europe and closed to casual visitors. The developed shore has sunbeds, a cafe and lifeguards.

What you actually see

• The warm lake - swimming at bath temperature under a limestone cliff.
• The cliff wall - the rock face where the cavern roof gave way.
• The spa shore - decked platforms, sunbeds and shallow entry steps.
• The cleaner fish - small fish that nibble at bathers in the shallows.

When to go

Winter and shoulder seasons are the treat, when the water is warmer than the air and the crowds are gone. July and August are busy and the entrance fee peaks.

Honest expectations

It is a managed commercial facility rather than a wild lake: entry is ticketed, sunbeds cost extra, and in summer it can be packed. The water carries a faint sulphur smell. The cave system is off-limits without technical certification.

Nearby

Vouliagmeni's beaches and the Athens Riviera run along the coast; Cape Sounion lies further south.