Saturnyne was the home of the Saturnyns. According to Rosanna Calvierri, Earth had an ocean like that of Saturnyne. The planet knew about and had considerable technology, including weather control, perception filters. They also knew about Gallifrey and the events of the Last Great Time War.
At some point in the planet's history, it fell to a mysterious crack in space and time that consumed its skies. The planet was lost to what Rosanna, a member of its species, referred to as "silence". A large number of its species escaped the planet through the crack to 16th century Venice. They planned to turn the city into the new Saturnyne. (TV: The Vampires of Venice)