Before April 1815, Mount Tambora stood as one of the tallest peaks in the Indonesian archipelago. The eruption -- VEI-7, the most powerful in recorded history -- obliterated the upper third of the mountain, collapsing it into a caldera roughly six kilometers across and over a kilometer deep. What had been a summit above 4,000 meters became a hollow approximately 2,850 meters high at its rim. The eruption ejected an estimated 10 billion tonnes of pyroclastic material, killed approximately 88,000 people on Sumbawa and Lombok, and pumped enough sulfur dioxide into the stratosphere to cool the planet for three years. Today the caldera dominates the Sanggar peninsula on Sumbawa's north coast, a vast bowl of rock visible from altitude, surrounded by slopes that have been slowly reclaimed by tropical forest.

In 2004, archaeologists used ground-penetrating radar to locate a small buried house on Tambora's flanks. Inside were the remains of two adults, along with bronze bowls, ceramic pots, and iron tools -- artifacts of a civilization erased so completely that media reports called it the Lost Kingdom of Tambora. The Tambora culture had its own language, now classified as a Papuan language unrelated to the Austronesian languages spoken throughout the rest of the region. Haraldur Sigurdsson, the volcanologist who led the excavation, intended to return to search for more villages and perhaps a palace. The eruption had buried these communities under meters of pyroclastic deposits, preserving them in a manner that drew immediate comparisons to Pompeii. Local folklore remembers the cataclysm differently: a ruler is said to have incurred divine wrath by feeding dog meat to a hajji and killing him.

Resettlement of the devastated area did not begin until 1907, nearly a century after the eruption. By the 1930s a coffee plantation had been established in Pekat village on the northwestern slope. Dense rainforest of Duabanga moluccana trees grew back at altitudes between 1,000 and 2,000 meters, and zoological surveys eventually documented over 90 bird species, including yellow-crested cockatoos, hill mynas, green junglefowl, and rainbow lorikeets. But the recovery has its own pressures. The yellow-crested cockatoo is hunted for the cagebird trade and is nearing extinction on Sumbawa. Orange-footed scrubfowl are hunted for food. Life returned to the volcano's slopes, but the ecosystem remains fragile, shaped as much by human appetites as by volcanic rebirth.

For over 150 years after the eruption, no one spent meaningful time on the caldera floor. Zollinger visited in 1847 but could only observe from the rim. Van Rheden did the same in 1913, and Petroeschevsky in 1947. The 2013 Georesearch Volcanedo expedition changed that. After nine days on the caldera floor, followed by a 12-day return expedition in 2014, the team documented the active venting of Doro Api Toi, the gases escaping under high pressure from the northeastern wall, and the previously unknown lava dome near the parasitic cone. This dome probably formed during the increased seismic activity of 2011-2012, though no one was on the caldera floor to witness it. The Indonesian government monitors Tambora from Doro Peti village using seismographs, and has designated a 58.7-square-kilometer danger zone around the caldera where habitation is prohibited. A broader cautious zone of 185 square kilometers encompasses seven villages that could be affected by lahars and pumice falls. An eruption comparable to 1815 would today threaten approximately eight million people.