Indonesia
Rising from the Flores Sea like a nearly perfect volcanic cone, Pulau Satonda is a small uninhabited island off the northern coast of Sumbawa that harbors one of Indonesia's most unusual natural phenomena: a saltwater crater lake nestled inside a dormant volcano, surrounded by coral reefs of pristine quality. The island sits within sight of Mount Tambora, whose catastrophic 1815 eruption—the largest in recorded history—ejected so much ash into the atmosphere that 1816 became the Year Without a Summer across the northern hemisphere. Satonda's own volcanic activity predates Tambora's apocalypse, and its crater has long since been breached by the sea, creating the remarkable inland marine lake that distinguishes this island from thousands of others in the archipelago.
The character of Pulau Satonda is defined by the surreal juxtaposition of its saltwater crater lake and the tropical sea that surrounds it. The lake, roughly one kilometer across, supports species of jellyfish that have evolved in isolation from the open ocean—non-stinging varieties that pulse through the warm, stratified waters in an ethereal ballet reminiscent of Palau's famous Jellyfish Lake. The crater walls rise steeply from the lake's edge, draped in tropical vegetation that includes towering banyan trees hung with flying fox colonies. These fruit bats, numbering in the thousands, emerge at dusk in a spectacle that darkens the sky above the crater as they depart for their nightly feeding on the mainland.
The marine environment surrounding Satonda is in superb condition, benefiting from the island's uninhabited status and its designation as a marine nature reserve. The fringing reef drops away steeply from a narrow shelf of coral garden, and the diversity of hard coral species rivals more famous Indonesian dive sites. Schooling fish congregate around the reef's outer edge where currents sweep past the island, and hawksbill turtles are frequently encountered grazing on sponges. Larger visitors include reef sharks patrolling the drop-off, occasional manta rays in the plankton-rich channel between Satonda and Sumbawa, and pods of spinner dolphins that ride the bow waves of arriving vessels.
Satonda's cultural significance extends beyond its natural wonders. Local Sumbawanese fishermen have long regarded the island as a place of spiritual power, and the shore of the crater lake is marked by wishing trees—branches hung with coral offerings left by visitors seeking blessings for safe voyages and bountiful catches. This practice, blending animist tradition with Islamic devotion, creates a landscape of delicate beauty where bleached coral fragments hang like wind chimes from ancient trunks. The island is uninhabited and has no facilities, but expedition vessels and dive liveaboards regularly anchor in the protected bay on the northern shore, providing a base for both lake exploration and reef diving.
Pulau Satonda is reached by boat from the port of Bima or Sape on Sumbawa, or by expedition cruise vessel navigating the Lesser Sunda Islands. The driest conditions prevail from May through October, with the calmest seas typically in September and October. Diving and snorkeling are possible year-round, though visibility peaks during the dry season. The hike from the landing beach to the crater lake takes approximately twenty minutes through dense forest on a sometimes slippery trail—sturdy footwear is essential. There are no shops, no fresh water, and no accommodation on the island; all supplies must be carried in and all waste carried out.