Hemmed in by water...and loving it

What effect does the confining aspect of water boundaries have on our great cities density and ability to create a truly urban sense of place? I posed the question about this relates to Manhattan in another thread, but the issue goes well beyond New York. Arguably our greatest American downtown areas are in New York, Chicago, San Francisco, and Boston....and all have used the confining nature of water boundaries to create their special urban environments: • Long and thin, the island of Manhattan has used its surrounding rivers to allow virtually all its areas to be "central" in nature...well, certainly from downtown to midtown and beyond a bit • Chicago's Loop was its own island like location: Lake Michigan to the east, the Chicago River to the north and west, rail yards to the south. Such confinement, in the 19th century, and the beginning of the 20th, created a highly centralized city with a density one would not expect for a city on the prairie. • San Francisco's peninsular location may well make it the most "set apart" of all US cities; no city has been able to create its own world due to its watery surroundings as SF. And the downtown region (if you include areas north of downtown up to the north waterfront around the Wharf, Ghirardelli, Pier 39, is set off by water on the east and the north. • Boston's original tad pole shape created an inviting density that is one of that city's hallmarks. Early Boston was almost the island that Manhattan is. Elsewhere, Philadelphia stretches between two rivers and Seattle benefits from an isthmus location. And if you really want to see how water works in a midsize city, try a trip to Madison, WI. This urban gem is built on an isthmus between two lakes. Its downtown is easily the most confined isthmus location in the nation. The result? A density and urban texture almost unthinkable in a city of its size....and a city that consistently ranks at or near the top of any list evaluating urban quality of life. Water hemming in our cities, it seems, is a very good thing.>