Beyond Trashi Chho Dzong at the north end of town, Dechen Phodrang stands on the site of Thimphu's original 12th-century dzong. Since 1971 it has housed the state lobra (monastic school), providing an education for more than 280 novice monks. If you visit during breaks between classes, expect lots of questions from the students!
The attractively proportioned main chapel contains murals dating back to the original 13th-century monastery, and the upper floor features a large figure of Zhabdrung Ngawang Namgyal. There is also a spooky side goenkhang (chapel dedicated to protective deities).