Atrios is locked in a long standing war of attrition with its twin planet Zeos. Due to the severity of the nuclear attacks from Zeos life on Atrios is led underground. Certain underground zones are sometimes irradiated due to roof collapses during severe nuclear attacks.
All metal on Atrios is needed, and even K-9 was very nearly recycled. As well as the recycling facility and the command centre there is also a hospital in which Princess Astra spent much of her time, although there was a love interest there in the form of chief surgeon Merak.
Six dynasties of the Royal House of Atrios have governed Atrios until the war allowed a Marshal, controlled by the Shadow, to take over. The fourth Doctor and Romana visited Atrios in their search for the sixth segment of the Key to Time. They managed to call a ceasefire and prevent the mutual destruction of Atrios and Zeos.
- Edge of the Helical Galaxy