- Central and reasonably priced accommodation (by US standards ie less than $US 250 a day) is available and maximises the time available for sightseeing etc.
- Empire State Building gives an excellent overview (literally) of the bottom half of Manhattan Island and nearby landmarks such as Liberty and Ellis islands.
- Museum of Modern Art
Needs more than one visit to even start to do justice to its collections.
- Natural History Museum
Good, but I was perplexed because I couldn't find the exhibit of the the giant squid and the whale fighting each other which was featured in (and gave the title to) the recent movie The Squid and the Whale.
- Staten Island ferry
A one hour free round trip which passes close to the Statue of Liberty and Ellis Island (though not as close as the Circle Line cruises) .
- Ground Zero
Worth a visit just to see the site: not only how much was destroyed and but also how so many buildings nearby were spared - check out the adjoining St Paul's Church with its almost intact graveyard and flower beds.
- Brooklyn Bridge
If possible walk across it from Brooklyn towards Manhattan and its skyline.
- Walk as much as possible (there aren't any steep hills) and use public transport when you need to move more a than a kilometre in a short time: $US7 buys an all day pass for the subway (which extends well beyond Manhattan Island) and the buses.