These impressive underground tunnels southeast of the village of Santa Rosa are more than 1km in length and were formed when the outside skin of a molten-lava flow solidified. When the lava flow ceased, the molten lava inside the flow kept going, emptying out of the solidified skin and thus leaving tunnels. Because they are on private property, the tunnels can be visited without an official guide. The tunnels have electrical lighting (you can also hire flashlights/torches). Tours to the lava tunnels are offered in Puerto Ayora.