Islamic art has a long tradition of decorative tilework, which was used to decorate the walls and other surfaces, both interior and exterior, of important buildings such as mosques and palaces. The sixteenth and seventeenth centuries were considered to be a “Golden Age” of Islamic tilework. Tile mosaics, in which glass or ceramic are organized into decorative patterns and then plastered, was one very popular technique. Another was known as dry cord tilework, also known as cuerda seca, first popularized in Spain during Umayyad rule. This process relies on large pieces of multicolored tiles, rather than smaller, individually colored fragments. Buildings such as the Imam Mosque to Isfahan, Iran, are covered in intricately patterned tiles in astonishing geometric and abstract forms.