The Imperial Enclosure or Imperial City is a citadel-within-a-citadel, housing the emperor’s residence, temples and palaces, and the main buildings of state, within 6m-high, 2.5km-long walls. What’s left is only a fraction of the original – the enclosure was badly bombed during the French and American Wars, and only 20 of its 148 buildings survived. Expect a lot of broken masonry, rubble, cracked tiling and weeds as you work your way around, but it's a fascinating site and easily worth half a day.
At a leisurely stroll, many of the less-visited areas are highly atmospheric and sublime. It's best to choose a day with decent weather, with late afternoon (when there are fewer visitors and the sun is setting) a superb time to visit. There are little cafes and souvenir stands dotted around. It's best to approach the sights starting from Ngo Mon Gate and moving anticlockwise around the enclosure. Restoration and reconstruction are ongoing.