Hi Aditya, Igatpuri is the nearest city to reach Ratangad Fort. Regular Maharashtra State Transport (MSRTC) buses are available from Mumbai, Thane and Nashik to Igatpuri and Bhandardara. You can hire a local, shared jeep from Igatpuri to Ratanwadi.
There is two wat 1) From Ratanwadi Village - Igatpuri to Bandardara to Ratanwadi
20 From Samrad Village- Igatpuri to Bhandardara to samrad village Both villages are accessible from state transport buses but bus frequency is very poor. Rather go by sharing vehicle.