Dongyue Temple is a Yuan dynasty Taoist temple, founded in 1319. Dongyue is dedicated to the god of Mount Tai, the Taoist god of the underworld. Often erroneously referred to as the god of hell—as Taoism as no concept of hell like that of Western belief systems—the god of mount is more like the overseer of the spirit world. This view is seen in the layout of the temple, which is divided into 76 departments dedicated to everything from bringing rain and healing sexually transmitted diseases, to dispelling ghosts and punishing evildoers (the above picture is of the department of water spirits).
Dongyue is an active Taoist temple, and a surreal experience that is both intriguing and a bit creepy. The temple also houses the Beijing Folk Customs Museum, which has both permanent and visiting exhibitions relating to the folk culture of China and Beijing.
The address of the temple is Dongyue Miao, 141 Chaowai Dajie, Chaoyang District, Beijing (东岳庙朝阳门外大街141号). It is located about 500 meters east of the Chaoyangmen subway station. Tickets cost 10RMB, 40RMB if you want a guide (not really needed as there are plenty of English captions). I also recommend visiting the temple during the Spring Festival (Chinese New Year celebration), as there is a tremendous old-style temple fair during that time.