Tradruk Temple is one of Tibet's oldest religious buildings, said to have been founded in the 7th century AD by the king Songtsen Gampo — before Samye, making it arguably the first Buddhist temple built in Tibet. It sits in the lower Yarlung valley, a short drive from Tsetang, and remains an active monastery today.
The complex has been rebuilt and expanded many times over the centuries, and the current structures are largely from the 15th century onward. The central hall houses excellent examples of Tibetan religious art, including gilded statues and painted murals. The atmosphere is one of quiet devotion rather than tourist spectacle — monks still chant here in the mornings. It's a worthwhile stop on any tour of the Yarlung valley sites.