Royal Observatory
Greenwich Park, London SE10 9NF
Web Site: www.rog.nmm.ac.uk
Tel: 020 8312 6565
Nearest Tube: Greenwich

Built by Sir Christpher Wren in 1675, the Royal Observatory museum explains the search for longitude . Exhibits include sundials, atomic clocks, and other pieces used by astronomers. Most famously perhaps, the Royal Observatory is the home of Greenwich Mean time.