Takht-e Soleyman (also known as Azar Goshnasp) is an ancient archaeological site located in the northwest of Iran. It is believed to have been a major Zoroastrian fire temple and royal residence during the Sassanian Empire (224-651 CE). The site is situated atop a volcanic peak at an altitude of 2,000 meters above sea level and includes several structures, including a palace, temple, and defensive walls.

The site's central feature is the large crater lake, known as the Lake of the Sun, which was considered sacred by the Zoroastrians. The temple complex was built around this lake, which was believed to have been created by a meteor strike. The complex includes several buildings, including the main temple, a fire temple, a palace, and a royal library.

The main temple is one of the most important structures at the site and is built on a raised platform. It is a circular structure with a diameter of 52 meters and a height of 38 meters, with an outer shell made of bricks and an interior chamber built of stone. The interior of the temple contains a large central hall with an octagonal pool in the center, which is believed to have been used for Zoroastrian rituals.

The palace at Takht-e Soleyman was built in the 13th century under the Ilkhanid dynasty and was used as a summer residence by the rulers of the time. It is located at the western edge of the site and features a large courtyard, several halls, and a tower that served as a lookout point.

In addition to its historical and architectural significance, Takht-e Soleyman is also known for its natural beauty, with its scenic surroundings and panoramic views of the surrounding landscape. The site was inscribed on the UNESCO World Heritage list in 2003, recognizing its importance as an outstanding example of the integration of natural and cultural elements.