When Portuguese ruled most of the west coast of India, they built fortifications and settlements along the coast and few inland to protect their trading ships and territory. These maps show where the fortifications were. Most or all of the fortifications are now in ruins however there are some pictures on this site of those ruins and forts.

Vasai Fort (Bacaim/Bassein fort)
Agashi customs house and Manor
Mumbai Islands (Bombay/Mombaim)
Asserim (Asheri/Asherigad)
Dahanu fort
Mahim Fort
Tarapur (Tarapor) fort
Chaul Korlai Fort