This one has been appreciated by many people I brought to visit it: it is a natural history museum with exhibitions on volcanoes, glaciers and life in Icelandic lakes, but it also includes a real-ice cave with -10° temperatures inside, showing how the interior of a real glacier would look like, and a thrilling planetarium projecting a celebrated aurora show which can be an ideal alternative to the real aurora if you visit in the summer and cannot hope to see the real thing!