La Palma is home to one of the three most important astronomical observatories in the world. (The other two are Hawaii and the Atacama desert in Chile.) The observatory sits at the top of the island, at the Roque de los Muchachos. It’s a fascinating place to visit, but it’s not normally open to tourists – they’re too busy doing science. However, you can sign up for a 90 minutes visit for 9€ per person. More details at http://starisland.co.uk/articles/visiting-the-observatory/