Hey Aniruddha, To see places in south Goa are :- Cabo de Rama - Ruins of Portuguese fort Colva beach Galgibaga beach Mahadev temple Cotigao wildlife sanctuary Three kings chapel Palolem beach Patnem beach Rajbagh beach Butterfly beach And never miss a boat ride in the waters also ... Happy Travelling Bro!!!
Hi Aniruddha, south Goa is comparatively less explored. The places you should definitely visit in south Goa are following
Agonda and Varca Beach
Dushsagar waterfall
Cabo de Rama Fort and Colva Beach
Madgao and Vasco de Gama
Also there is a very interesting post about discovering south Goa, i'm attaching that post with this comment, you can check it out and plan your trip.