Lipno is an artificial dam in South Bohemia.
The dam was built due to frequent flooding and subsequent damage to the settlements (including Český Krumlov). Completed in 1960, it also features a hydroelectric plant. Nowadays, the artifial lake area and its surroundings are a popular spot for camping, tourism and summer sports.
Most of the activities are grouped nearby the Lipno nad Vltavou town (east coast of the lake), which also is home to many luxurious(-ish) recreational houses, marina, beach, big camp and others.
The road 39 from Ceske Budejovice/Cesky Krumlov is the most frequented. Especially before the summer weekends the road is very congested.
An alternative road via Pribram and Pisek is possible, though somewhat more winding.
Multiple border crossings with Austria are available - e.g. Lichtenberg and Freistadt are nearby. The former one is useful in winter to access the nearby Hochficht ski area.
Most people come here for walking in nature and biking/inline-skating.
To shorten the path, ferry is available between various towns (Bližší Lhota, Černá v Pošumaví, Frumburk, Lipno nad Vltavou) and few shores. Especially the one between Frýdava and Frymburk is convenient - it connects both ends of the inline track.
Boat rentals are also available.
The surrounding Sumava national park (esp. if you are staying at the west of the lake) provides many nice hikes both in summer and winter.
Cesky Krumlov is a historic town on the road to/from Central Bohemia and well worth the visit.