Yonghe Temple, more commonly known as the Llama Temple.
It’s the largest Tibetan Buddhist temple in China, part of the Geluk, or Yellow Hat school of Buddhism. That’s the main school of Mahayana Buddhism, which is the dominant of the two main branches of Buddhism.
Mahayana Buddhism, including the Yellow Hat School, is primarily focused upon something called the bodhisattva: buddha/adherent that is focused on achieving Nirvana and breaking the cycle of Samsara only after all other sentient beings in the universe have done so first. That’s actually who the Dalai Llama is: he’s not the head of his school, but is the reincarnation (the 14th at present) of the Avalokitesvara, basically the first bodhisattava. There’s still a throne in one of the main halls of the Yonghe Temple, reserved for whoever is the current Dali Llama.
The coolest sight to see in Yonghe Temple is a more than 50 foot tall statue of Buddha carved out of a single piece of sandalwood. Unfortunately, like all the halls in Yonghe Temple, no photography is allowed. They’re filled with delicate artifacts dating back more than 400 years old and photography from the huge number of visitors can be damaging. But I did get a few good shots of the outside courtyards.