Cueva de los Verdes is a yawning, 1km-long chasm, which is the most spectacular segment of an almost 8km-long lava tube left behind by an eruption that occurred 5000 years ago. As the lava ploughed down towards the sea, the top layers cooled and formed a roof, beneath which the liquid magma continued to slither until the eruption exhausted itself. Guided tours, lasting about 45 minutes and available in English, take place every 30 minutes or so.
On the tour you walk through two chambers, one below the other. The ceiling is largely covered with what look like mini-stalactites, but no water penetrates the cave. The odd pointy extrusions are where bubbles of air and lava were thrown up onto the ceiling by gases released while the boiling lava flowed; as they hit the ceiling and air, they hardened in the process of dripping back into the lava stream.
Anyone with severe back problems might think twice about entering the cave – there are a few passages that require you to bend at 90 degrees to get through, although only very briefly.
Concerts of mainly jazz and blues are held here from September to April.
