The Reykjanes peninsula being mostly lava doesn't hold water well and lakes are few. The lakes that are there don't have any surface rivers flowing in or out of them and in fact there aren't any on the peninsula. Kleifarvatn is the biggest lake in the region and is quite interesting with Krisuvik, a thermally active area, at it's end. Around Reykjavik there are some small lakes popular for trout fishing. The Blue Lagoon, not a lake really but a natural hot pool, is near the town of Grindavik. It has an unearthly light blue colour and there are swimming facilities and other services there.