The ancient name was Prayag. Also known as sangam nagari, Tirth Raj . After that comes new religion by Samrat Akbar Deen E Ilahi in Prayag its name become Allahabad. In Allahabad mix three river holly ganga, yamuna abd sarswati that is called sangam.
Here a fort is also. In fort a akshay vat tree also situated. Here so many historical places like Anand Bhawan, allahabad university building, hanuman mandir. Saraswati ghaat etc. Every year Magh mela is held and every 12 year Kumbh mela. Its a very good historical place