Decently sized (74 hectares/183 acres), it was once a deer preserve maintained for royal amusement; a herd of them still have 5 hectares (13 acres) at their disposal. It’s been a Royal Park since the 15th century, although the boundary wasn’t formally defined until the early 1600s when James I erected a brick wall around it, much of which still survives. On top of its clean-swept main hill are marvelous views of the Canary Wharf district, and the world-famous Royal Observatory, commissioned in 1675 by Charles II, serves as the intersection point for the Prime Meridian, making it the center of Greenwich Mean Time. Most people combine a visit here with the many other museums of Greenwich.