The Shah mosque (also known as Masjed-e Shah or Imam mosque) is located on the southern side of the Naqshejahan square and is one of the most beautiful mosques in the world. It was built in the Safavid period in the early 17th century. It is registered along with the Naqshejahan square as a UNESCO world heritage site. Its walls are covered by seven-color mosaic tiles and calligraphic inscriptions.