The Temple of Heaven is a complex of buildings used for Heaven worship. It was built in the 15th century, and is a Taoist temple (Heaven worship predates Taoism–though the Temple doesn’t.) The most distinctive building, the Hall of Prayer for Good Harvests–shown only partially in the picture–was built without any nails or spikes.
It’s located in a beautiful park south of central Beijing. The park has a rose garden and is a popular hangout for people doing tai chi, playing instruments, and dancing.