For a taste of old London, board the modern red Routemaster number 15 bus at Limehouse DLR station and switch to a 1950s heritage version of this iconic vehicle at Tower Hill. It takes 15 minutes to get to St. Paul’s Cathedral, Christopher Wren's 17th-century baroque masterpiece. From there, it’s a short, scenic walk across Millennium Bridge to the contemporary works at the Tate Modern museum.