Northwest

Sanjay Gandhi National Park
Local Stn. Borivali, Borivali, Mumbai +91 22 2842 1174. Check out this relatively unknown national park, situated in north Mumbai. It's in Borivali and serves as the lungs of Mumbai. It's quite famous for its leopards and the caves inside the park. Open 7:30AM-7:30PM.

Within the park are three fun activities: pedal boating, a toy train ride that runs over a bridge and through a tunnel, and a "safari" bus ride into the park to view tigers and lions. Tickets for each activity are sold on site.

Kanheri Caves
Local Stn. Borivali — Borivali, Mumbai is a nice place to visit for history enthusiasts. This is a complex of Buddhist temples cut out of the rock. 9AM-5:00PM. Entry Fee is 5 Rs. per person.
Aarey milk colony
is another green pocket of Mumbai. You can take a tour of the milk production plant and have a picnic outside.
Manori
tiny island off Marve beach near Malad
Rs. 2.50 per person for the ferry, additional charges for vehicles.

This is a small beautiful island with nice beaches, but dangerous for swimming. The beach on the northern side is cleaner. This is a nice place to spend the weekend though. It has a couple of hotels see under sleep. To get here from Malad station, you can take an auto for Rs. 50 or a BEST bus and reach Marve, from where you can board a government-operated ferry. Make sure to try the sea-food here. Also be sure to book in advance, as the rooms get filled up, especially over the weekend.