Answer

If you mean Bhagwan Mahavir, the place most commonly given for the maximum Chaturmas is Rajgir, also called Rajgriha, in Bihar. Jain sources and government publications note that he spent 14 Chaturmas there. ( mea.gov.in)

Explanation

Rajgir is considered a very important Jain pilgrimage place because of its close connection with Bhagwan Mahavir’s spiritual life. ( mea.gov.in)

Takeaway

So the short answer is: Rajgir. ( mea.gov.in)