Isabela Island

Isabela is by far the largest island in the Galápagos [1] and accounts for half of the archipelago’s total land mass at nearly 4,600 square kilometers. At 100 kilometers long, it’s four times the size of Santa Cruz [2], the next largest island.

The landscape is dominated by six intermittently active volcanoes—from north to south: Wolf (1,646 meters) and Ecuador (610 meters), which both straddle the equator, Darwin (1,280 meters), Alcedo (1,097 meters), Sierra Negra (1,490 meters), and Cerro Azul (1,250 meters), which was the latest to erupt, in May 2008.

The island’s only port, Puerto Villamil, where most of the population of 2,000 lives, is slowly turning into a tourism hub, though on a much smaller scale than Puerto Ayora and Puerto Baquerizo Moreno. There are plenty of visitor sites near the port as well as excursions inland to the volcanoes, but many of the best coastal sites are on the western side of Isabela, only accessible to cruises.

As the giant of the archipelago, it’s only fitting that Isabela has one of the largest populations of giant tortoises, which feed on the abundant vegetation in the highlands. There are five separate subspecies here, one for each volcano (excluding tiny Volcán Ecuador). The slopes of Volcán Alcedo have the biggest population—more than 35 percent of all the tortoises in the archipelago.

The west coast of the island has large populations of whales and dolphins as well as flightless cormorants, which dive down into the cool waters in search of fish and no longer need their wings. Isabela also has the largest populations of Galápagos penguins, although numbers fell dramatically as a result of the 1998 El Niño.

The tortoise population here has suffered considerably. Whalers used to hunt them, and more recently thousands of feral goats have eaten their vegetation; cows and donkeys trample on their eggs. Volcanic eruptions and a fire started by people that raged for five months in 1984 have also ravaged the landscapes. Things are improving, though, particularly after 100,000 goats were successfully eradicated in a huge government operation in the past decade, mainly employing Australian hunters in helicopters.

Sierra Negra

The best excursion to take from Puerto Villamil and perhaps the most impressive geological sight in the entire archipelago is the hike up to the active Sierra Negra, Isabela’s oldest and highest volcano. The last eruption was in 2005 and took geologists by surprise, so you can’t trek right to the crater.

However, there are two excellent treks—the shorter is to Volcán Chico, a fissure of lava cones northwest of the main crater. On this side, there is less mist and rain, offering spectacular views over the north of Isabela and across to Fernandina. This trek takes about four hours and is usually a combination of hiking and horseback riding.

The longer trek is to Las Minas de Azufre (Sulfur Mines). It takes about 6–7 hours in total and is tougher, particularly in the rainy season, when it gets very muddy. Your toil will be rewarded, however, with fantastic views of the crater, which at 10 kilometers in diameter is the second-largest in the world after Ngorongoro in Tanzania. The hike culminates in a dramatic descent into the yellow hills of the sulfur mines that spew out choking gas (hold your breath).

Both treks can be booked with the tour operators in the port, but note that the longer trek is less common, so booking ahead is essential. Nautilus (Antonio Gil and Las Fragatas, tel. 5/252-9076, www.nautilustour.com [3]) charges $40 pp. Wilmer Quezada is a particularly good local guide (tel. 8/687-8626 or 5/252-9326).