Its difficult to know exactly when and how Rajasthan originated. It is said that the Indus Valley Civilization, one of the world’s first and oldest, was in parts of what is now Rajasthan. Kalibangan, in Hanumangarh district, was a major provincial capital of the Indus Valley Civilization, now part of Pakistan. It is believed that Western Kshatrapas were Saka rulers of the western part of India (Saurashtra and Malwa: modern Gujarat, Southern Sindh, Maharashtra, Rajasthan). They were successors to the Indo-Scythians and were contemporaneous with the Kushans who ruled the northern part of the Indian subcontinent. The Indo-Scythians invaded the area of Ujjain and established the Saka era (with their calendar), marking the beginning of the long-lived Saka Western Satraps state. Matsya, a state of the Vedic civilisation of India, is said to roughly corresponded to former state of Jaipur in Rajasthan and included the whole of Alwar with portions of Bharatpur.