Isabela Island comprises fifty-eight percent of the Galápagos archipelago's total land mass, yet its population remains under three thousand. Six shield volcanoes, five still active, merged over millennia to form the seahorse-shaped island. Wolf Volcano, the archipelago's highest point at one thousand seven hundred seven metres, last erupted in 2015, sending lava flows to the coast. The island's western flank plunges into the Cromwell Current, creating nutrient upwellings that sustain one of the Pacific's richest marine ecosystems. Puerto Villamil, the island's sole settlement, was founded in 1897 as a penal colony. For decades, prisoners quarried lime and tortured giant tortoises for oil. The corrals closed in 1959, the year Ecuador declared the islands a national park. Today, the flamingo lagoons behind the village occupy the same brackish ponds where convicts once hauled stone. Isabela Island day trip itineraries radiate from this compact waterfront: east to Tintoreras Islet, where Humboldt penguins nest in lava crevices, or west to Los Túneles, a labyrinth of submerged arches carved by cooled pahoehoe flows. Tintoreras lies fifteen minutes by panga from Puerto Villamil. White-tipped reef sharks circle a shallow channel at slack tide; marine iguanas bask on black basalt; blue-footed boobies dive in synchrony offshore. The islet's name derives from tintorera, local Spanish for the reef sharks that patrol the split. Los Túneles, thirty minutes southwest, demands calm seas. Snorkelers glide through cathedral-like tunnels beneath mangrove roots, encountering green sea turtles, seahorses, and hunting penguins. Surface intervals reveal the skeletal bridges of collapsed lava tubes. Galápagos National Park regulations limit group size to sixteen per guide and prohibit touching wildlife. All landings require a certified naturalist. The two-hundred-dollar conservation fee, paid once upon archipelago entry, funds trail maintenance, invasive-species eradication, and tortoise breeding programs. Isabela's relative isolation has preserved ecosystems already extinct on Santa Cruz. Flightless cormorants, found only on Isabela and Fernandina, dry their vestigial wings on the rocks at Punta Moreno. Land iguanas, reintroduced in 2019 after a century's absence, now patrol the caldera rim of Sierra Negra, the second-largest active crater in the world at nine by ten kilometres.