Hi Dhwani, There are several amazing places you can choose to visit around Mumbai like Matheran, Alibaug, Kashid, Kolad, Karjat, Lonavala, Mulshi to name a few. You can find more details about the weekend gateways from Mumbai in the article attached below: Keep exploring!
Check out Bhandardara, dist. Ahmednagar. It's an amazingly beautiful place. There's mountains all around. Bhandardara is situated in the midst of Sahyadri range. You must visit this place once at least. Check out The Land Of Wanderlust (TLOW) website..... https://thelandofwanderlust.com/