M5V-801 was a planet in the Pegasus galaxy which contains a Stargate. One part of the continent is prone to earthquakes, as the village can experience at least four tremors a day.
In 1988, the Genii took control of the planet, and forced the simple villagers to become miners. The Genii turned the planet into a mining facility to mine for a certain ore that were a great benefit to them. Years later, the ore has been mined out, and the Genii abandoned the planet. To top off the seismically unstable surface, the air supply around the village contained several contaminants, mainly from the ore the village was mining. In 2008, the Atlantis expedition were made aware of the planet's problems, and decided to evacuate the villagers to a more stable, safer part of the continent. However, in order to do so, the villagers made a list of demands a "mile and a half long". Colonel Samantha Carter, along with Dr. Jennifer Keller and Dr. Rodney McKay came to this planet to negotiate with the inhabitants, but on the way to the village, they fell through a hole to the highly structurally unstable Genii mining facility. The trio eventually managed to have escaped the facility, by scaling down by rope, to a mine shaft, before the facility collapsed and fell down the deep chasm. (SGA: "Trio")