Since this is your arrival day, keep it easy and let Mumbai come to you. Start at Marine Drive Promenade for that first real “I’m in Mumbai” moment — the walk is best in the evening when the sea breeze kicks in and the whole curve of the bay starts glowing. From here, it’s an easy, very local-feeling shift to Girgaum Chowpatty, where you can snack like a Mumbaikar: pav bhaji, bhel puri, sev puri, and roasted corn are the usual go-tos, with most items landing around ₹50–150. It’s lively, slightly chaotic in the best way, and the perfect place to wander for about an hour without needing a plan.
Head down to Bademiya in Colaba for dinner — expect a wait if you arrive at peak dinner time, but the kebabs and rolls are exactly the kind of satisfying first-night food that works after a flight. Budget roughly ₹700–1,200 per person depending on how hungry you are. After that, stroll over to Gateway of India; it’s especially atmospheric at night, when the monument is lit and the waterfront feels calmer than during the day. Finish with a short walk around The Taj Mahal Palace Lobby / Apollo Bunder, where the façade of The Taj Mahal Palace gives you that classic old-Mumbai introduction. If you still have energy, linger around the plaza for a few photos and then call it an early night — tomorrow is when you can start digging deeper into the city.