This altar – to the west of the Temple of Heaven – was the site of solemn imperial ceremonies and sacrificial offerings. Located within what is called the Hall of Jupiter (太岁殿; Tàisuì Diàn) – the most magnificent surviving hall – is the excellent Běijīng Ancient Architecture Museum, which informatively narrates the elements of traditional Chinese building techniques.
Glance at any pre-1949 map of Běijīng and you can gauge the massive scale of the altar, which was built in 1420. Today, many of the altar's original structures survive and make up a tranquil and little-visited constellation of relics. The museum offers the chance to brush up on your dǒugǒng (brackets) and sǔnmǎo (joints), get the low-down on Běijīng’s courtyard houses, while eyeballing detailed models of standout temple halls and pagodas from across the land. There’s a great scale model of the old walled city and English captions throughout. On Wednesdays the first 200 visitors get in free.
