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