Those who want to discover the secret of La Palma's good water supply should take the hikes to Los Tilos and the Marcos y Cordero springs. The latter leads through 13 tunnels that were once laboriously cut out of the rock by hand to get to the water, which is so valuable for La Palma. The top of La Palma consists mainly of volcanic tuff, which is very porous and leads the water well. At an altitude of about 1.000 m, however, there is a massive lid of basalt rock that was originally formed many thousands of meters below sea level under the great pressure of the water and was brought to this height with the enormous eruption that La Palma once created. As basalt is waterproof, springs have been created at this interface that carry water all year round and provide us with drinking water of excellent quality. But the path to the springs was steep and surrounded by almost impenetrable jungle. For example, water channels and tunnels were built in particularly steep places to bring the water to the settlements. You can easily walk along these canals, as they have a gradient of only 3%. However, the tunnels are narrow and partly low. For this hike you should take waterproof shoes, a torch and better also a good head protection, as well as a rain jacket, because in the last tunnel the water already falls from the rock walls and runs everywhere on the ground. Nevertheless, an adventure that is worthwhile and will once again bring you closer to the diversity of La Palma.