Made a trek to a fort near Lonavala called Visapur (one of the Maratha forts) with a group of trekkers from Mumbai (who call themselves the 'Fort Capturers'). Had an awesome time. The fort overlooks the Mumbai-Pune express-way and is really impressive.
Photos: Trek to Visapur
To get there: We caught the Indrayani Express at VT at 6am and got down at Lonavala (~3 hours journey). Then took a local to Malvali village (~10 mins journey). The fort overlooks the village. Takes atleast 2 hours to climb.