6-Day Western Islands: Sierra Negra's Giant Caldera

Most Galapagos itineraries begin here. Baltra's airport is the world's first fully ecological airport, run on solar and wind power and built largely from recycled materials, including old oil pipes repurposed into the terminal structure. Land iguanas, wiped out here by the 1950s and reintroduced through a decades-long breeding program, now number in the hundreds again, some right around the airport grounds. From the terminal, a short bus transfer brings you to the pier for the panga ride out to your ship.

A geology stop first and foremost. A wet landing on a white coral-sand beach leads out onto a pahoehoe lava field that flowed less than a hundred years ago, its surface still holding the ropy, swirled texture it cooled into, a favorite for photographers. Tiny pioneer plants are just beginning to colonize the cracks in the rock. Bring your camera for the landscape rather than your binoculars here.

Sierra Negra's caldera stretches 10 km north to south and 9 km east to west, one of the largest volcanic calderas on Earth. The more commonly walked route to Volcan Chico crosses relatively recent lava flows with sweeping views toward the volcanoes of Isabela and neighboring Fernandina; a longer trek reaches a system of active fumaroles known as the Sulfur Mine. This is a geology-and-scenery visit, and wildlife isn't the focus here.

There's no landing here. The whole visit happens aboard a zodiac. The route passes the Marielas Islets, home to the largest and most important Galapagos penguin colony in the archipelago, before easing into a cove ringed by red mangroves. Flightless cormorants perch at the water's edge, sea turtles surface nearby, and golden rays glide beneath the boat now and then. It's one of the best places in the islands to watch this much wildlife without ever stepping ashore.

A zodiac ride along Tagus Cove's cliffs is the first stop, tracing walls carved with the graffiti of sailors and whalers going back over a century. Charles Darwin himself anchored here in 1835. Watch the rock for Galapagos penguins and flightless cormorants before you land and set off on a gently climbing trail, roughly 30 minutes each way, to a viewpoint over Darwin Lake, a crater lake saltier than the ocean itself. Along the way, look for land birds that are easy to miss: ground and tree finches, yellow warblers, large-billed flycatchers, and, with a little luck, the tool-using woodpecker finch. Land iguanas and giant tortoises sometimes cross the path as well. Back at the water, most visits close with a dinghy ride or a snorkel along the submerged cliff wall, depending on the day's plan, with another good chance at penguins and cormorants gliding by.

A quiet landing on Santiago's western coast, best known as a nesting ground for Pacific green sea turtles, who come ashore to lay their eggs between December and June.

A tiny, flat islet of white coral sand between North and South Seymour, Mosquera is best known for its resident sea lion colony, sprawled across the beach for much of the day. Shorebirds and lava herons work the shoreline fairly reliably, and sharks and rays are a possibility for anyone snorkeling or diving nearby.