A glass dome perched on top of six former hot-water tanks on the wooded Öskjuhlíð hill. The viewing deck wraps the whole way around and gives you the best free panorama in the city — the bay, Mount Esja, the airport, and the rooftops of central Reykjavik. Inside there is a planetarium, an ice-cave walk, and a wax-and-multimedia exhibit on Icelandic nature, plus a cafe and a more expensive rotating restaurant.
It is a thirty-minute walk from downtown or a quick ride on bus 18.