The Regent's Mosque, built in the 18th century by Karim Khan Zand, is best known for its vast prayer hall: 75 metres long, 36 metres wide, its roof supported by 48 twisted columns, each carved from a single block of stone. The spiral fluting catches the light differently at different times of day. The tilework in the iwans is outstanding — deep blue and turquoise in the classic Zand style.
The mosque is attached to the Bazaar-e Vakil, so you can combine both in a single visit.