The square is so big that polo matches were once played across it - and the stone goal posts are still there at each end! Today people stroll, cycle and share picnics across the wide open space, while two grand mosques, a royal palace and a covered bazaar line the edges. In the middle sits a long rectangular pool, reflecting the blue-tiled domes like a mirror.
The tile-work is extraordinary. Craftspeople called 'kashi-karan' spent years cutting tiny pieces of coloured ceramic and fitting them together in swirling patterns of flowers, geometric shapes and fine calligraphy. Some domes use more than 470,000 individual tiles. The shade of blue - a deep turquoise - became so famous that it is sometimes simply called 'Isfahan blue'.
The covered bazaar at one end of the square is a maze of arched brick corridors full of carpet sellers, spice merchants, goldsmiths and tea-houses. It has been trading for centuries. The echoing sounds, the smell of fresh cardamom and saffron, and the soft clinking of copper-smiths hammering bowls make it one of the most exciting shopping streets in the world.