Mumbai

Mumbai (Bombay until 1995) is India's economic capital — population 21M, the most populous Indian city + financial center + home to Bollywood (1,500+ Hindi-language films/year, world's largest film industry by volume; produces more films than Hollywood). The Gateway of India (1924 yellow basalt arch built to welcome King George V on 1911 visit) anchors Colaba's tourist heart, facing the iconic 1903 Taj Mahal Palace Hotel (target of 2008 Mumbai terrorist attacks; now refortified). Marine Drive ('Queen's Necklace,' 3.5km Art Deco curved promenade lit at night) is THE Mumbai night photo. Elephanta Caves (UNESCO 7th-century rock-cut Hindu temples on island, 1h boat from Gateway). Dharavi (Asia's largest slum, 1M people in 2.5km², 7-figure economy via leather + pottery + recycling, portrayed in Slumdog Millionaire — Reality Tours runs ethical visits with 80% revenue to community). Mumbai street food (vada pav + pav bhaji + bhel puri were invented here).

Iconic Mumbai cuisine: Vada pav (potato fritter in bun, $0.40-1 — Mumbai's "burger"; Ashok Vada Pav canonical), Pav bhaji (vegetable mash + buns, $2-5 — Sardar canonical), Bhel puri (puffed rice + chutneys, $1-3), Bombay sandwich (multi-layer veg sandwich, $1-2 — Royal Sandwich), Bombay duck (dried fish, $5-10 — actually a fish, not duck), Trishna's butter pepper garlic crab ($25-40), Mumbai chai ($0.30-1).

Bottom line: Mumbai is India's most cosmopolitan city + Bollywood + canonical street food. 3-4 days hits Gateway + Bollywood + Dharavi + markets.