Sevastopol, also known as Sebastopol, (TV: War of the Sontarans) was a city on the Crimean Peninsula. The Seventh Doctor and Ace were stranded there from September through November 1854 during the Siege of Sevastopol. (AUDIO: The Angel of Scutari)
In an alternate timeline created by the Sontarans during their Flux assault, it was the site of a battle between Sontar and Great Britain. The Thirteenth Doctor, along with Mary Seacole and General Logan, worked together to drive off the Sontaran threat, and the timeline was later aborted. (TV: War of the Sontarans)