The Central region is where most first-time visits happen by default — it holds the skyline, the shopping, the museum belt, and Chinatown, all within a few MRT stops of each other.
Marina Bay
The postcard version of the city: Gardens by the Bay, the Marina Bay Sands SkyPark, and the Merlion, all facing each other across the water. Almost everything here is walkable in a single loop, and it's the single best area for a first afternoon.
Orchard Road
Singapore's shopping spine — a two-kilometre stretch of malls ranging from mass-market to genuinely high-end. Not much reason to linger unless shopping is the point, but it's a useful, well-connected base.
Chinatown & the CBD
Temples, wet markets, and hawker food sit a short walk from the glass towers of the financial district — one of the sharper old-versus-new contrasts on the island. Chinatown Complex is one of the best hawker centres in Singapore, not a tourist-only version of one.
The museum belt
National Gallery Singapore, the Asian Civilisations Museum, and the Peranakan Museum sit within walking distance of each other along the river — a good rainy-afternoon plan.