Four periods are recognised in Pakistani architecture: pre-Islamic, Islamic, colonial, and post-colonial. With the beginning of the Indus civilization around the middle of the 3rd millennium BCE, an advanced urban culture developed for the first time in the region, with large buildings, some of which survive to this day. Mohenjo Daro, Harappa, and Kot Diji are among the pre-Islamic settlements that are now tourist attractions. The rise of Buddhism and the influence of Greek civilisation led to the development of a Greco-Buddhist style, starting from the 1st century CE. The high point of this era was the Gandhara style. An example of Buddhist architecture is the ruins of the Buddhist monastery Takht-i-Bahi in Khyber-Pakhtunkhwa.