On Santa Cruz island you will find different attractions such a snorkeling, giant tortoise reserves, bird and whale watching, and also explore the lava tunnels.
As you might know, the Galapagos archipelago is mainly composed of volcanoes, still active or not, and was formed thousand years ago by a the movement of tectonic plates. During the eruption of those volcanoes, the lava has formed tunnels in which you can now walk into, without danger. The magma is fossilized and allows you to walk trough. The longest tunnel which you can visit in Santa Cruz is 2km long.
The lava tunnel we chose is located in the Rancho Primicias, a natural reserve where you can observe giant turtles. To get there we have two options: take a private tours for $30, a taxi for $20 or take the bus and walk for $1. We took the bus because it is very cheap, and easy, even tough it took us 1h30 driving and 45 minutes walking. But still it is part of the experience.
You will first have to reach the bus station located in the northern part of Puerto Ayora. You can access directly from the harbor, walking up the Main Street, on your left you will see the bus stop "Parada de autobus". As I said the bus ticket is $1. The driver was very friendly and told us were to get down, in a small city. From there we walked 30 minutes to the entrance of El Chato reserve. Luckily, on the way a truck picked us up and dropped us at the entrance of the reserve.
The entrance fee is $5 for an unlimited time. You can walk in the park where giant tortoise are eating fruits, mud bathing of just sleeping in the high grass; and also visit the lava tunnels, the main reason why we came here.