Three reasons are attributed to the greatness of Vraj.
1. It is the land where divine being Sri Krishna has manifested and it is Lila Bhoomi - A place where HE performed his Lilas or sports.
2. It has historical importance also as it was ruled by Surasena in ancient times.
3. It is the land where a special cologuial language called "Vraj" is spoken here.
Sri Krishna's Lila Bhoomi :
Sri Krishna has manifested as "Purna Purushottama" in Vraj. He has performed several chidlhood sports that put everyone into wonder here known as Bala Lilas and Kishore Lilas. In all he stayed here for eleven years and 52 days in Vraj. The places he has sported in are Gokul, Brindavan, and Nandagam. Then he stayed for fourteen years in Mathura. There he performed Lilas as a youth of velour. In all twenty-five years were spent in Vraj Lila and Mathura Lila on this Holy Land.
Through thousands of years have passed by, people still feel the presence of Sri Krishna in these places. Hence Vraj has become a holy place for all Hindus. Thousands of Hindus pay their homage by visiting Vraj.
District SuraSen :
The limits of this district changed during the passage of time. The traveler from China - Hue - en - Sand wrote that the places presently known as Mathura, Agra, Bharatpur and the northern parts of Madhya Pradesh were included in the kingdom of Surasen.
Thereafter when the boundaries of the Kananj Kingdom expanded the area of the kingdom of Surasena began to divide.
At present greater part of Vraj is included in the district of Mathura. A few parts were joined to Bharatpur district in Rajasthan. A small part of it was annexed to Naryana. Vraj Bhoomi is said to contain 84 kosas. But in reality it is more than that.
The land where Vraj Bhasha is spoken :
Puranas described the land of Vraj as having circular form. But when we take into consideration the parts where the language of Vraj Bhasha is spoken we will realize that the present Vraj Bhoomi is not fully circular.
Many take the meaning of Mandal as a place of inhabitation. As such Vraj Mandal indicates the place where "Vraj" is spoken.
The extensions of the limits of Vraj is explained in a work called "Vraj Bhakti Vilas", written about the year 1560 A.D.
Ita Barahad Uta Sonahad
Hta Surasena Ko Gam
Braj Choresi Kosmain
Mathura Mandal Gram ||
According to these 8 lines : "Vraj's limits on the east extended to the village called Barahad of district AliGadh; The western boundary extended to Sona Nadi in the district of Gudagaon; The southern limits went upto Vateswar village in the district of Agra, and the northern limits reached Bhushanvan in the taluka of Shergadh. In all these parts people talked in Vraj Bhasha.
Now a days these limits were curtailed to some extent.
Are Vraj and Mathura one or different ?
In Varaha Purana, divine being HIMSELF has described about the extension of Vraj Mandal thus - "My Mathura Mandal is 20 Yojana - known as 80 Gaun & Yojan add four Gaun (Kosa) of Mathura nagari it will come to 84 gaun or Kosa".
This gives us an idea of Mathura nagari not being in Vraj Mandal. Mathura and Vraj Mandal are two places situated side by side.
The same opinion is expressed in Sri Bhagavatji also.
1. Raja Parishit has asked Sri Sukadevji "What has Kesava (Sri Krishna) done while staying in Vraj and Madhupuri ?"
2. In different chapters of 10th canto Vraj and Mathura were dipicted as separate places.
Basing on these statements Sri Mahaprabhuji has come to the conclusion that :
1. Vraj is transcendental Goloka and
2. Mathura is an Adhyatmic (Spiritual) Tirtha (Holy place).