a Greater London borough on the Thames: site of a Royal Naval College (now used as the National Maritime Museum), including Inigo Jones ’ Queen ’s House (1617), and of the original Royal Observatory designed by Christopher Wren (1675), accepted internationally as the prime meridian of longitude since 1884, and the basis of Greenwich Mean Time. Pop: 223 700 (2003 est). Area: 46 sq km (18 sq miles)