An iconic temple structure within the captol.
About the Temple of Heaven
Originally built in the 1400's, the Temple of Heaven was originally used as a place where emperors prayed for good harvests.
The shape was designed to represent the unity of heaven and earth and is now one of the city's most popular tourist sites.
Photographing the Temple of Heaven
If you're hoping to get 'that' empty photo, I'd really recommmend grabbing a tripod and then combining the photos after to remove people. The entire complex will fill up with tourists extremely fast so at best you'd get 1 or 2 quick shots.
If you don't want that tripod shot I'd say if you stand on one of the buildings to the side of the main centre you'll be able to get a portrait without the people below you, or you could rush to the back side with the archway - that side gets busy up the slowest.