A small rock in the Atlantic: Visiting the Observatory, 2009

GranTeCan, the huge new Spanish telescope

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. You can visit the mountain top and see the buildings from the outside any day of the year. But please note:

Days only, not nights. The William Herschel Telescope could see a candle on the moon, and the MAGIC telescope is even more sensitive. They really don't like car headlights. Some years ago there was an incident some years ago where a bus shone its lights right at the Herschel's dome. Now there's a barrier across the road which is shut a half an hour after sunset, and raised around dawn.
The road to the observatory is usually blocked for a few days each winter, by snow or landslides. Use your common sense. If the sign at the bottom of the mountain road says it's blocked, don't go up. I once rescued a couple of German tourists who'd spent the night in the car in the drainage ditch, after going past the sign, thinking that the weather couldn't be all that bad in the Canaries. It can. That night it was thick fog, 60 mph winds, and -5C. Thank God they didn't try to walk, because they'd have frozen to death for sure.

Since the MAGIC gamma ray telescope doesn't have a building, you get quite a good view from the outside. You can get fairly close by parking on one of the heliports (the bottom left as you go up the hill). From there, a footpath goes closer, and there's a display panel that explains how the telescope works.

If you want to see inside, you need to go on a guided tour. In 2009 they will hold 28 open days, each with only one group. Each visit starts with a visit to the MAGIC gamma-ray telescope, followed by one other telescope, and lasts about two hours. Visits must be booked in advance, by calling the receptionist at the Institute of Astronomy on (00 34) 922 425 703. And yes, the receptionist speaks English. Book early -- the places go fast. But no children under 12 allowed.

They also hold private visits, usually for schools or visiting astronomers. You can email your request to adminorm@iac.es. I believe the person who reads the email, speaks English. To be honest, they're unlikely to organise a visit for the average tourist, but if there's a visit organised anyway, you might be able to tag along. Cross your fingers!