
The Lake Vouliagméni is situated on the western coast of Attika peninsula, on the way to go to Sounio from Athens.
We got "Γ1 (gamma ena)" bus from Pireas, which runs hourly and takes about three quarters of an hour, to get there (€0.5). From Athens you can get the same bus as the one takes you to the Cape Sounio via Gryfada, or come to Neo Faliro by bus, metro or tram to get Γ1.
The lake, situated just by the sea, is famous for its curative power; it said to be effective against rheumatism and all sorts of skin diseases. For this reason, the majority of the visitors are often elderly. And for some unknown reason, there seems to be some younger visitors from the Eastern Europe.
Notice that it is prohibited to bath in the lake with sun-lotion on.

The entrance fee is €7 (Summer 2006; there are reduced fees for children and elder citizens) and it includes the use of the changing room, shower, toilets, parasols, and chairs (although you might not find any free parasols during the peak season peak hours).
Waiters bring you coffee and light bites on request, but the price tends to be higher than the standard (€5 for a Nescafe Frappé). There is also a taverna on the same site, and, if you prefer a nicer place, there is also a restaurant (called, O Lamplos) just on the other side of the highway by the sea.

In the lake there are a lot of small black fish commonly called "Kalógries". The word means "nuns" in Greek, and must come from its black colour. If you put your feet in the water, these small creatures come to touch you.
In the photo below is the coast line of Vouliagméni, just outside the lake. Near the lake, I did not see any bathing facilities, but people do swim here. You many need a parasol, as there isn't so many places you can avoid the sun.
References
- Robin Barber, Greece (Blue Guide), London/ A&C Black, 2001 (revised reprint of the 1995 sixth edition), pp. 124-125.