Perlan

This guide to Perlan in Reykjavik starts with an odd detail: six geothermal water tanks sit under its glass dome, though only four still hold water. It traces the site's history from the first tank raised on this hill in 1939 to feed hot water across Reykjavik, through a 1980s decision to rebuild the aging cluster into something new. You'll hear what happened inside the tanks that no longer hold water, including a chamber built for icy exhibits. Look for the ring of six tanks as you walk the dome.