Bradleys Meridian is the reference point for Longitude today and has been since 1750.
Markers exist for the prime meridian (agreed in 1884) and the Bradley meridian (1750), but modern GPS devices apparently place it about 50m to the East of the planetarium.
OG: Maze Hill 0.63km
LRTS: Cutty Sark 0.76km
LRTS&OG: Greenwich 0.84km
6am - dusk.
Always check details regarding opening hours, accessibility and pricing before travelling.