This is the Great South Gate (Nandaimon) of Shitennō-ji temple. Shitennō-ji was originally constructed in 593, but the actual buildings have been rebuilt many times over the ensuing centuries. The last complete rebuild took place in 1963, so while not brand-new, the temple buildings are quite young by comparison to other sites. Many consider Shitennō-ji to be the first Buddhist and oldest official temple in Japan.