You must go to Marine Drive - a horse cart ride, some kachchi kairi would be great. Hunt up an Irani Cafe that will take you back in time. If you're going now, it's Kala Ghoda time. You must take that in too!
There's the Gateway of India and Colaba Causeway.
Come a little North and there's Bandra Bandstand,Mt.Mary's Church, Hill Road for Shopping. Finally, Prithvi theatre in Juhu for a show and a meal and you're done!