The Metropolitan line is a London Underground service that connects Aldgate in the City of London, the capital's financial heart, with Amersham and Chesham in Buckinghamshire, with branches to Watford and Uxbridge. Coloured purplish red on the tube map, the line serves 34 stations in . The section between Aldgate and Baker Street is shared with the Circle and Hammersmith & City lines, between Rayners Lane and Uxbridge with the Piccadilly line, and between Harrow-on-the-Hill and Amersham with Chiltern Railways. Just under 67 million passenger journeys were made on the line in 2011/12. The line is one of the only two London Underground lines to cross the Greater London boundary, the other being the Central line.