Marina Bay is where Singapore made the statement it wanted the world to receive. The land was reclaimed from the sea, the towers were built over forty years, and the result is a financial and civic district that is genuinely impressive in a way that can be separated from whether you think it was worth the cost to build it. Marina Bay Sands is an extraordinary piece of engineering regardless of what you think about the casino attached to it. The Helix Bridge, the ArtScience Museum, the skyline from across the bay at night: Singapore designed this to be seen and it succeeded.
Gardens by the Bay is the piece that does not get reduced to a photograph. The Supertree Grove is the thing in the photograph, but the two Cooled Conservatories are the things worth an afternoon. The Cloud Forest in particular, a mountain inside a sealed glass structure with a waterfall running down its face, is one of the more improbable spaces in Southeast Asia.
The CBD around Raffles Place and the waterfront has the best preserved colonial architecture in the city: the Fullerton Hotel (formerly the General Post Office), the Old Parliament House, the Victoria Theatre. It is worth an hour on foot with no particular agenda other than noticing what was built before the towers arrived.
Every visitor at least once, because Marina Bay is what Singapore built to show the world who it is. Architecture and design enthusiasts who want to see the Moshe Safdie buildings and the Helix. Families with older children who can handle Gardens by the Bay at full length. Anyone who wants to understand the city's economic story in spatial terms.
Not the right base for more than one or two nights unless you are here for business. Marina Bay is a district of events and landmarks, not a neighbourhood to live in. The hotels are excellent and expensive; the residential feel is zero.
The Cloud Forest inside Gardens by the Bay: buy the ticket for the Cooled Conservatories, not just the grounds. Go after four in the afternoon. The walk from the Merlion across the Helix Bridge to the Marina Bay Sands promenade for the view back to the Fullerton and the colonial waterfront. The Fullerton Hotel lobby for the building rather than the rates. National Gallery Singapore on St Andrew's Road, the former Supreme Court and City Hall converted into a museum of Southeast Asian art, which is the best museum in the city and the one most visitors skip. Lau Pa Sat, the Victorian cast-iron market building in the CBD, for satay on the street outside after dark.