The Jameh Mosque is a veritable museum of Islamic architecture and still a working mosque. Within a couple of hours you can see and compare 800 years of Islamic design, with each example near to the pinnacle of its age. The range is quite stunning: from the geometric elegance of the Seljuks, through to the Mongol period and on to the refinements of the more baroque Safavid style. At more than 20,000 sq metres, it is also the biggest mosque in Iran.