Try the hidden Village part inside national park only in rainy season it's beautiful.be careful to ensure you will not travel solo or only two three girls.also you can explore the Karjat side in rains for a day picnic.sabarwal farms is Awesome for overnight picnic but I am sure it must not be operational this year.keep travelling and exploring
These are the best lesser known places in Mumbai are:
Hasnabad Dargah, Byculla
Gilbert Hill, Andheri
Gables, Colaba
Toy Street In Fort
Maharashtra Nature Park, Dharavi
Golfa Devi Mandir, Worli
Banganga Tank, Malabar Hill
Lush Green Farms & Gardens, Vile Parle
Mumbai have its own beautiful history. so many places in Mumbai has unexplored. if you want to explore Mumbai find out hidden gems watch gost Mumbai chi series on youtube.