The Old Town has preserved its medieval plan and many Reformation-era buildings. One end is closed by the castle and the main artery, the Royal Mile, leads away from it; minor streets (called closes or wynds) lead downhill on either side of the main spine in a herringbone pattern. Large squares mark the location of markets or surround public buildings such as St. Giles' Cathedral and the Law Courts. Other notable places nearby include the Royal Museum of Scotland, Surgeons' Hall and McEwan Hall. The street layout is typical of the old quarters of many northern European cities, and where the castle perches on top of a rocky crag (the remnants of an extinct volcano) the Royal Mile runs down the crest of a ridge from it.