Ahicchatra was the capital of northern Pāñcāla. Droṇācārya took this northern half of the Pāñcāla kingdom for himself as his guru-dakshiṇā (the teacher’s gift), after Arjuna captured Drupada and brought him before him.

Droṇa divides Pāñcāla

Droṇa divided Pāñcāla into two parts. He kept the northern half, with Ahicchatra as its capital and as the seat of the Brahma district along the Gaṅgā. He gave the southern half back to Drupada, with Kāmpilya as its capital. So Droṇa became a king occupying half of what had been Drupada’s kingdom.

Droṇa’s capital

After Arjuna captured Drupada, Droṇācārya took Ahicchatra and the northern half of Pāñcāla as his own seat. At that moment he was no longer only a brāhmaṇa teacher. He was a king with land, subjects and a capital. He returned Kāmpilya and the southern half to Drupada. Through teaching, Droṇa had won a kingdom.

Sources

Mahābhārata, Ādi Parva, Sambhava Parva, Chapter 138