The 195-square-mile, volcanic San Cristóbal, in the eastern Galapagos, is the second-most visited island in the archipelago after Santa Cruz. Cruisers follow in the footsteps of Darwin here, indulging in geology expeditions, snorkeling, and wildlife viewing — boobies, frigate birds, marine iguanas. The main settlement is Puerto Baquerizo Moreno, also the provincial capital for the Galapagos. Cruise ship visitors are typically assigned to a fixed circuit of guided excursions such as hiking and swimming, though a little free time might be made for independent exploration, too.