Lava Caves (Grutas De Lava)

Pico is a young volcanic island, and beneath its lava fields lie tunnels left by flows that crossed the landscape long ago. The best known is the Gruta das Torres, near Criação Velha on the north side of the island, which is the longest lava tube in the Azores, with a total length of about five kilometres, although only a short section of around four hundred and fifty metres is open to visitors. It was formed roughly fifteen hundred years ago when a stream of molten rock from the volcano's flanks poured downhill. The surface of the flow cooled and hardened into a crust, while the lava inside continued to run until it drained away, leaving a hollow, tunnel-shaped cave.

The visit is by guided tour, which usually lasts around an hour. Visitors are given helmets with lamps and descend through an opening in the ground into the tube, which is cool and damp at a fairly constant temperature through the year. The route follows the floor of the tunnel, at times high and wide, at others low enough to make you duck. Guides explain how the lava flowed and how the cave was formed, and they point out the features that show the process. The roof and walls are marked with lines left by the falling level of the lava, and the ceiling is hung with lava stalactites, small drips of rock that solidified as they fell. Rounded lava balls, rippled ropy surfaces, and glassy patches can be seen on the floor and walls.

Within the caves the silence is striking, and at a point in the tour the lights are switched off briefly to show the complete darkness. The experience is a good introduction to volcanic geology, particularly for families with children, and it is not physically demanding, though the ground is uneven and the roof is low in places. Sturdy shoes with grip are essential, and a warm layer is useful since temperatures are lower than outside.

Bookings are recommended in summer, and prices and times vary by operator, so check before you arrive. The caves are not far from the road around the island, and they combine well with the lava vineyards and natural swimming pools along the coast and with a drive to the foot of the mountain.

The caves suit curious visitors of all ages, geology enthusiasts, and families. Allow about one and a half hours, including travel to the entrance.