Isabela is the biggest island of the archipelago and occupies about 60% of all the land area of Galápagos. It was formed by the volcanoes Cerro Azul, Sierra Negra (Santa Tomás), Alcedo, Darwin, Wolf and Ecuador that conflated to one island. All except Volcano Ecuador, which is older, are still active today. Even though Isabela has several visiting sites, it is not very frequented by tourists.
Most of the landing sites are on the west coast and only faster boats make this long journey. The small port Puerto Villamil (about 3,000 inhabitants) is the main settlement on the island. There is also a small airport. This town is a good base if you plan to stay longer on Isabela. The area offers beautiful beaches and it takes a 20-minutes walk to get to Laguna de Villamil, one of the favorite spots for birdwatchers on the islands. Flamingos can be seen here as well as about twenty different kinds of wading birds.
If you like mountains you can also hike up Volcano Sierra Negra (1,490m) from Puerto Villamil. A van takes you up to the village Santo Tomás (20 km) and from there you can hike or ride up on horseback to the rim of the volcano (9 km). On the top you have a magnificent view over the 10 km-wide caldera. There is a trail that takes you to some active fumaroles. This area is home to short-eared owls, finches, flycatchers and Galápagos hawks.
Muro de las Lágrimas (Wall of Tears) is a visitor site west of Puerto Villamil. This wall of lava rocks has been built under harsh and abusive conditions by convicts (8 m high, 200 m long). The penal colony has been closed in 1959 but the wall still stands as a monument to this infamous chapter of the islands history. Today it is a good place to observe lava lizards closely and watch out for birds, especially Galapagos finches and hawks.
The following sites can only be visited by boat:
On the southern west coast, Punta Moreno is situated. On the rocky shores you can usually see penguins and a great variety of shore birds (including flamingos if you are lucky). There is a trail leading through the lava rocks. The Bolívar Channel between the Islands of Fernandina and Isabela is often frequented by whales. So you might want to look out for circles of smooth water – they may be whale “footprints”.
In front of Bahía Elisabeth (Elizabeth bay) there are the Mariela Islas where you are often welcomed by penguins. This bay is known for its variety of undersea life. Snorkelers encounter marine turtles and rays. But as the water is very clear you can also observe them from a panga (dinghy). The coastline is covered with mangroves that are home to seabirds and herons.
Urbina Bay is located at the base of Volcán Alcedo. In 1954 there was an uplift that raised the shoreline suddenly as far as 1 km out to the sea. A trail takes you to a coral reef that is now up on dry land. This is a good site to see flightless cormorants, marine iguanas and pelicans.
Farer up to the north, Tagus Cove is located. A panga (dinghy) ride along the coast offers, next to a variety of seabirds, historical graffiti. In former time it was a favorite anchorage ground and the sailors scratched the names of their vessels into the cliffs. The tourist trail passes Laguna Darwin. a salt water lagoon, and takes you to various lava formations and a ridge whit a spectacular view.
At the northernmost point of Isabela Island lies Punto Albermarle; this was once a US radar base. Today it is known for flightless cormorant that can be observed from your boat (no landing/visitor site). A good place to snorkel is nearby Punta Vicente Roca, at the base of Volcano Ecuador.