Which is the oldest architecture found in Gujarat?

Directions: Read the following passage and answer the question that follows.

Gujarat is a diverse and dynamic state with fascinating archaeological sites, distinctive and magnificent architecture, and exquisite handicrafts and tribal cultures. A variety of natural attractions ranging from welcoming beaches to the desert wilderness of Rann of Kutch and the rich forested slopes around the hill station of Saputara.
The state’s architecture, especially the intricately carved temples, majestic mosques and mausoleum complexes, finely carved wooden havelis, and step wells that are so beautifully sculpted that they look like subterranean palaces. Gujarat has some of the most substantial remains of the Harappan Civilisation in India at Dholavira and Lothal. It is also associated with great leaders like Mahatma Gandhi and Sardar Patel.