The Bella Lagoon
I find the Tourist Things That You Must Do when visiting a country often disappoint, but the Blue Lagoon didn't at all. It's wonderful - super-high-tech facilities combined with the most soothing, amazing and bizarre swimming hole in the world.
They say the Icelanders are incredibly laid back about just about everything, but a major bugbear is foreigners not bathing correctly before entering their chemical-free swimming pools. So I was careful to follow the instructions, and strutted into the communal shower area in all my glory, only to find everyone else wearing trunks.
Perhaps there's an updated guide book which says the major bugbear is foreigners strutting into the communal shower area in the skud.