Why is Prayagraj called Tirthraj?

Prayagraj is called Tirthraj (King of Tirthas) because the scriptures — including the Matsya Purana, Padma Purana, Vayu Purana, and Mahabharata — unanimously declare that its spiritual merit exceeds that of all other pilgrimage sites combined. Lord Brahma performed his first creative sacrifice here, and the Triveni Sangam concentrates the power of three sacred rivers in one point.