Rajmachi is a small village located near Karjat. There are two forts which are known for trekking. One can enjoy this place in every season.
Summer: To watch fireflies
Monsoon: To see waterfalls and greenery
Winter: To camp and enjoy the cold winds.
I have personally been to this place 4 times, it's like a second home for me now.
I am going for the fireflies trek on this 22nd May. If anybody is interested, you're most welcome :D