Perched above Paro Dzong is its ta dzong (watchtower), built in 1649 to protect the undefended dzong and renovated in 1968 to house the National Museum. The unusual round building is said to be in the shape of a conch shell, with 2.5m-thick walls.
Displays include an impressive collection of thangkas, both ancient and modern, depicting Bhutan's important saints and teachers, as well as fearsome festival masks grouped according to their tsechu dances. There's a natural-history gallery with a 3D map of Bhutan, while the Heritage Gallery contains such oddities as an egg laid by a mule and a horse horn attributed to Guru Rinpoche, plus a few original iron links from the iron bridge at Tamchhog. An underground tunnel is said to lead from the watchtower to the water supply below.