Coudenberg Hill (now Place Royale) was the site of Brussels’ original 12th-century castle. Over several centuries this was transformed into one of Europe’s most elegant and powerful palaces, most notably as the 16th-century residence of Holy Roman Emperor Charles V. Around the palace, courtiers and nobles in turn built fine mansions. The vast complex was destroyed in a catastrophic 1731 fire, but beneath street level the basic structure of the palace’s long-hidden lower storeys remains.
Whole stretches of the medieval street layout are now discernible, though little atmosphere remains. The subterranean site is entered from Musée BELvue and you emerge near the Old England Building.