About 5km south of Thimphu on the old road to Paro and Phuentsholing, the handsomely proportioned Simtokha Dzong was built in 1629 by Zhabdrung Ngawang Namgyal. The site is said to mark the spot where a demon vanished into a rocky outcrop, hence the name Simtokha, from simmo (demoness) and do (stone). The site was also a vitally strategic location from which to protect the Thimphu valley and the passage east to the Dochu La and eastern Bhutan.

　　Officially known as Sangak Zabdhon Phodrang (Palace of the Profound Meaning of Secret Mantras), Simtokha is often said to be the first dzong built in Bhutan. In fact, there were dzongs in Bhutan as early as 1153, but this was the first dzong built by the Zhabdrung, and was the first structure to incorporate both monastic and administrative facilities. It is also the oldest dzong to have survived as a complete structure. Just above the dzong is Bhutan's Institute for Language and Culture Studies.

　　During its construction Simtokha Dzong was attacked by an alliance of Tibetans and five Bhutanese lamas from rival Buddhist schools who were opposed to the Zhabdrung's rule. The attack was repelled and the leader of the coalition, Palden Lama, was killed. In 1630 the Tibetans attacked again and took the dzong, but the Zhabdrung regained control when the main building caught fire and the roof collapsed, killing the invaders. Descriptions of the original buildings at Simtokha Dzong were provided by two Portuguese Jesuit priests who visited in 1629 on their way to Tibet.

　　The fortress was restored and expanded by the third desi (secular ruler), Mingyur Tenpa, in the 1670s, and it has been enlarged and modified many times since. The fine murals inside have been restored by experts from Japan. The squat, whitewashed dzong looks more fortress-like than most, and the only gate is on the south side (though the original gate was on the west wall). As you enter, note the murals of the four guardian kings – Vaishravana (north), Dhritarashtra (east), Virudhaka (south) and Virupaksha (west) – protecting the four cardinal directions, and the jewel-vomiting mongoose in the hand of the yellow King of the North.

　　The utse (central tower) is three storeys high, and prayer wheels around the courtyard are backed by more than 300 slate carvings depicting saints and philosophers. The large central figure in the central lhakhang is of Sakyamuni, flanked by the eight bodhisattvas, and the ceiling is hung with an incredible array of dhvaja (victory banners) in brightly coloured silk. The dark murals inside this lhakhang are some of the oldest and most beautiful in Bhutan and the walls are adorned with embroidered thangkas (religious pictures).

　　In the western chapel are statues of Chenresig, green and white Taras, and an early painting of Zhabdrung Ngawang Namgyal. Check out the tigers' tails and guns hanging from the pillars in the eastern goenkhang, a protector chapel dedicated to the guardians of Bhutan, Yeshe Goenpo (Mahakala) and Pelden Lhamo.