What's the must-see thing in Mumbai?

The building that tells you more about Mumbai than any guidebook is Chhatrapati Shivaji Maharaj Terminus, the railway station the British completed in 1888 at the southern tip of Fort district. It carries roughly 3 million passengers per day through arched corridors where pigeons roost in stone brackets 40 feet overhead and the ticket hall smells of chai, printer ink, and warm metal from the tracks below. The stained glass and carved sandstone make it look like a cathedral. That is not an accident. Frederick William Stevens designed it to announce Bombay as an imperial capital. Go around 10am. Before that, the commuter crush is serious, bodies pressed tight enough that you feel the heat of strangers' shoulders through your shirt. After 11am, the light through the west-facing rose windows fades. No ticket required to walk the main hall. The platforms are public, through the regular entry gates.

Walk 2km south from CSMT along Dadabhai Naoroji Road and you reach the Apollo Bunder waterfront, where the Gateway of India has stood since 1924. The basalt arch was built as a ceremonial landing for King George V, and it ended up being the spot where the last British troops left India in 1948. Worth noting, the monument itself takes about 10 minutes. The reason to come is the surrounding 500 metres. The Taj Mahal Palace Hotel sits directly behind it, open since 1903, and its lobby is accessible to visitors who pass through security screening. The harbour smells of diesel and salt. Touts will approach you about boat rides to Elephanta Island. Ignore the ones at the gate. The legitimate MTDC ferry counter is at the jetty itself, 250 rupees round trip, about $2.65 at current rates. The crossing takes an hour each way, and the 5th-century cave temples on Elephanta are worth it if you have a full half-day, but not worth rushing.

Between CSMT and the Gateway, set back from Mahatma Gandhi Road behind a garden of mature palms, Chhatrapati Shivaji Maharaj Vastu Sangrahalaya has occupied the same Indo-Saracenic building since 1922. Admission is currently 100 rupees for Indian residents, 650 rupees (about $6.85) for foreign nationals. The Gandhara Buddhist sculpture collection on the ground floor is the reason to visit. Stone heads from the 2nd century with expressions so specific they look like portraits. The natural history wing upstairs feels dated, glass cases with taxidermy from the 1930s, but the miniature paintings gallery on the second floor holds Mughal and Deccani works you will not see outside the V&A or the Met. Air-conditioned throughout, which matters when it is 34°C with 77% humidity outside. Plan 90 minutes. The museum closes at 6pm, with last entry at 5:15pm.

All three sit within a 2km walk of each other in South Mumbai, between Fort and Colaba. That matters because Mumbai is a city where distances lie. A place 15 minutes away on Google Maps might take 90 minutes in a taxi during the evening crawl north on the Western Express Highway. For your first day, stay south of Churchgate station and walk. The pavements are uneven and often broken, so wear shoes with real soles, not sandals. Mumbai is currently in monsoon season. The drizzle today is light, but June storms can dump 50mm in under an hour, flooding low-lying streets around Hindmata Junction and Sion within minutes. Carry a compact rain jacket, not an umbrella. The wind will invert it before you get any use from it. The Kala Ghoda neighbourhood between the museum and CSMT has the best concentration of cafes for a mid-walk pause. Cafe Mondegar on Metro House has been serving cold Kingfisher since 1932, and the Mario Miranda murals on its walls are a Mumbai institution. A pint costs around 350 rupees, about $3.70.