CC Madhya 9.310

tāpī snāna kari’ āilā māhiṣmatī-pure
nānā tīrtha dekhi tāhāṅ narmadāra tīre
Word for word: 
tāpī — in the Tāpī River; snāna kari’ — taking a bath; āilā — arrived; māhiṣmatī-pure — at Māhiṣmatī-pura; nānā tīrtha — many holy places; dekhi — seeing; tāhāṅ — there; narmadāra tīre — on the bank of the river Narmadā.
Translation: 
Śrī Caitanya Mahāprabhu next arrived at the banks of the river Tāpī. After bathing there, He went to Māhiṣmatī-pura. While there, He saw many holy places on the banks of the river Narmadā.
Purport: 

The river Tāpī is also known as Tāpti. The river’s source is a mountain called Multāi, and the river flows westward through the state of Saurāṣṭra and into the Arabian Sea.

Māhiṣmatī-pura (Maheshwar) is mentioned in Mahābhārata in connection with Sahadeva’s victory. Sahadeva, the youngest brother of the Pāṇḍavas, conquered that part of the country. As stated in the Mahābhārata:

tato ratnāny upādāya purīṁ māhiṣmatīṁ yayau
tatra nīlena rājñā sa cakre yuddhaṁ nararṣabhaḥ

“After acquiring jewels, Sahadeva went to the city of Māhiṣmatī, where he fought with a king called Nīla.”