Trongsa Dzong was first built in 1647, and it was from this dzong (fortress) that the first two Bhutanese kings ruled the country. The structure is strategically located on a steep slope commanding an extraordinary view of the Mangde River, approximately in the middle of the Kingdom of Bhutan.

Narrow stone stairs, alleys, and corridors connect the buildings at all levels of the fortress, creating a veritable labyrinth on the slope.

Within the walls of the dzong are 25 temples dedicated to Tantric deities, a watchtower (Ta Dzong) dating back to 1652, a printing shop producing religious texts following an ancient tradition, and a museum honoring the Wangchuck dynasty. In addition to its military importance, Trongsa Dzong was a major administrative and religious centre, still housing around 200 monks during the winter months.

The historic fortress was badly damaged by an earthquake in 1897, and eventually restored in 1927 and 1999. It now annually hosts Trongsa Tsechu, a 5-day religious festival where traditional costumes and masks are deployed for the dances. The date of the festival falls in December or January, in accordance with the Tibetan Lunar Calendar.

Reference: https://www.atlasobscura.com/places/trongsa-dzong