Located in Kaushambi, Prabhosa Hill is one of the most important sites for Buddhists in India. It is believed to be the place where Lord Buddha spent his sixth Rains Retreat, a three-month period when monks observe silence and do not travel. The hill was also known as Mankula in ancient times and finds a mention in the travel memoirs of Chinese traveller Xuanzang, who visited the place in the 7th century and found a stupa constructed by emperor Ashoka. The rocky terrain of the hill is dotted with caves and the largest of them is Sita's Window. Historians suggest that this might be the exact spot where Lord Buddha stayed during his visit to Prabhosa. On climbing the top of the hill, tourists can get commanding views of River Yamuna and the quaint temple town of Prabhosa.