Rising out of nowhere, in the stark desert landscape of Yemen is the Dar al-Hajar, or the Rock Palace.
Perched atop a pinnacle in the Wadi Dhahr valley, the palace, widely acknowledged as an architectural marvel, appears to grow out of sheer rock, hence the name.
The Dar al-Hajar was built in 1786 by the scholar Ali bin Saleh Al-Amari, who was a renowned cleric, poet and master of geometry and astronomy.
In the 1930s, the five-storey building was converted into a summer palace for Yemen's rulers at the time.
Out of the five storeys, only three are completely visible while the rooms, kitchens and facilities are hidden below ground level.
Featuring a grand tower at its pinnacle, the palace is a popular example of Yemeni architecture.
Now a museum, it is located about 14km from the capital Sana'a, and visitors can enter the palace for a fee.