A glass dome sits on top of six cylindrical tanks that hold most of Reykjavik's hot-water supply, on a low hill on the south side of town. Inside is an excellent nature museum — a real ice cave that runs through the underbelly of the building, full-scale displays on glaciers, volcanoes, geothermal energy and Icelandic wildlife, and a planetarium that screens a Northern Lights show.
The top floor is an outdoor observation deck with a 360-degree view: the city below, Mount Esja across the bay, the Reykjanes peninsula to the south, and Snæfellsjökull (the glacier of Jules Verne's Journey to the Centre of the Earth) faintly visible 120 km away on a clear day.