Since the beginning of the Republic's sorties to Pikachu space, Vish'tam was thought to have been an arid, gaseous, hostile world. However, the Vojan Memorial Probe Program debunked that theory as soon as its second probe, VMPP-A-001-1B, descended into Vish'tam's dense atmosphere. It found an area ripe for colonization, with no native lifeforms. By 55 BBY, an inhabited station, PIONEER 1, had been placed in the atmosphere.
Renamed Vish'tam City, by 21 BBY PIONEER 1 had become a thriving metropolis of over 21,000 people, sprawling for over 1000 kilometers in the Life Band. After the Declaration of a New Order, Vish'tam City and its associated gas mining installations were seized by the Empire, and used as a staging ground for actions against Eloque and Kamino.
However, the native Tamins were less than thrilled about being controlled by the Empire. In 12 BBY, a radical group called the Free Vish'tam Movement initiated one of the worst disasters in galactic history. Attacking at night, they sabotaged the city's repulsorlift generators, causing the entire city to begin a headlong dive into the poisonous atmospheric layer below. Although many organizations mounted rescue attempts, within three days it had reached the point of no return. 12,550 of the city's 19,910 citizens died in the fateful plunge.