Orchha and Gwalior in Madhya Pradesh are a hidden gems u can go through my write up to know more about both the places at https://travellingfeets.travel.blog
If it's unexplored it would be North East and East India. I would suggest you to go Manipur
sikkim
guwahati
meghalaya
gangtok
nagaland
shillong
cheerapunji
Darjeeling
mizoram
agartala