Pulau Una-Una is an extremely remote island adjacent to the Togean National Park in the Gulf of Tomini, in Central Sulawesi, close to Kadidiri island, a world famous dive site.

Una-Una was formed by the short, broad Colo Volcano, whose summit rises just 500 meters above sea level, with a 2 kilometer wide caldera. UnaUna is a lush and scenic island and is indeed a direct result of the Colo Volcanoís eruption. One interesting by-product of the islandís volcanic nature is that unlike the pure, white sands of the other islands in TominiGulf, Una-Unaís beaches are a striking black.

Throughout history, only three eruptions have been recorded from Mount Colo, with two of them causing damage. In 1983, after over 80 years of dormancy, a powerful eruption burst from Mount Colo. Thick, yellow clouds rose 5 kilometres into the air, with volcanic ash reaching as far as East Kalimantan. Pyroclastic flows swept across the island, destroying everything in its path. Many settlements were completely devastated and hot clouds destroyed all plant species on the island. Only a narrow strip of vegetation and villages along the islandís east coast remained undamaged.

Six months prior to the eruption, the volcano began to show activity, giving the islandís residents the opportunity to be gradually evacuated to the surrounding islands. There were no casualties, and Mount Colo has not erupted since.

Una-Una remained uninhabited for some time, but after a few years, people gradually began returning to rebuild their lives. Initially, they only came to start agricultural production, but over time they once again began building homes. Although Colo volcano is still active and could erupt at any time, this did not dampen the desire of UnaUnaís previous inhabitants to return home.

Several changes have taken place on the island since the eruption. As a sort of blessing in disguise,the volcanic ash and lava which covered UnaUna has created an island of extremely fertile soil. Additionally, its deer population has increased drastically to an estimated tens of times higher than before. The phenomenon may have possibly been caused by the demise of many deer predators. Island residents now raise elk for every day needs such as food and clothing.