The Greenwich Meridian Line marking Longitude 0° as the centre of world time is defined by a line running across the Royal Observatory courtyard. Endorsed by international agreement in 1884 as the Prime Meridian of the world, it attracts visitors from around the globe to stand astride the line that divides East and West.
You can see the 17th century rooms occupied by the first Astronomer Royal, the observation room with its early Tompion clocks and displays on the development of improved navigation at sea that led to Britain's leadership in world exploration and trade for several centuries.
The most important, intricate, marine timekeepers of John Harrison, the carpenter/inventor, are all on display alongside the earliest accurate clocks used to establish Greenwich as the world standard for accurate time signals. These Greenwich clocks became the centre for sending the time signal throughout Britain and later by cable to synchronise with other nations.
To get there from the Americana; take the Jubilee lind southbound from Baker Street to Canary Wharf and change to the DLR. Take the DLR southbound to Cutty Sark, the museum is signposted from there.