Seeing the developments of architectural styles throughout centuries in only one structure is possible in the Masjed-e Jame or congregation mosque of Isfahan. Dating back to the 9th century, the mosque has been expanded over the years, adapting different architectural styles, and most notably the four-iwan courtyard style of the Sassanid palaces. Additionally, the double-shell ribbed dome of the mosque has become an inspiration for subsequent constructions of mosques. The mosque was recognized as a UNESCO World Heritage Site in 2012.