City Thameslink /ˈsɪti ˈtɛmzlɪŋk/ is a railway station in the City of London, England. The platforms are underground with a southern entrance on Ludgate Hill just off Ludgate Circus, and a northern entrance on Holborn Viaduct. It is in Zone 1 on the Thameslink route between Blackfriars and Farringdon. Although a through station, for ticketing purposes it is considered a central London railway terminus for journeys to and from the south.