Tivoli

Tivoli was the most conquered planet in the galaxy. It was inhabited by a species of rodent-like humanoids. They were one of the oldest civilisations in the galaxy and simply let invaders do as they wished. Their anthem was "Glory To  " and their cities were designed to be comfortable for the invading armies. It was green in colour when seen from space. (TV: The God Complex) Its capital city had a sign saying "If you occupied us, you'd be home by now." (TV: Before the Flood)

By 1969, the Dominators had conquered the Tivolians, (PROSE: Mutually Assured Domination) but they were later conquered by the Fisher King and his people in 1970, where they ruled for ten years, before being liberated by the benevolent Arcateenians in 1980. The Tivolians did not take kindly to have those oppressing them removed from power. The Arcateenians became so irritated by the Tivolians that they chose to enslave them as well. An undertaker, Albar Prentis, was sent by them to bury the Fisher King on a "barren, savage outpost" in accordance with Arcateenian custom. However, the Fisher King had survived his supposed death but was eventually defeated and killed by the Twelfth Doctor. (TV: Before the Flood)

Gibbis was a native of Tivoli, whose job involved planting trees so that invading forces would be shaded during their marches. (TV: The God Complex)

Behind the Scenes

 * In a deleted scene for Before the Flood, Albar Prentis explains that the Arcateenians liberated Tivoli from the Fisher King and his forces by raising the planet's sea level and drowning them, something that worked because the Fisher King came from a barren world. The Tivolians were taken off the planet in slave ships for their own protection while this occurred.