NEW ORLEANS

If the levees break again and the nation gives up the fight to save the lowest parts of New Orleans, the Big Easy would be reduced to a sliver of land along the Mississippi River, leaving the French Quarter and the oldest neighborhoods as the only places on dry ground.

NEW YORK

At the southern tip of Manhattan, sea water would inundate Battery Park City, now home to 9,000 people. Waves would lap near the base of the new Freedom Tower. Beachfront homes from the Rockaways to the Hamptons, could be swamped.

MIAMI

You can kiss goodbye the things that make South Florida read like an Elmore Leonard novel: the glitz of South Beach, the gator-infested Everglades, and some of the bustling terminals of Miami International Airport.

BOSTON

Fourth of July celebrations won’t be the same. The Esplanade, where fireworks watchers gather, would be submerged, along with the Hatch Shell where the Boston Pops stages its annual concert. Some runways at Logan International Airport will be partially covered, and the neighborhoods tourists know best would be smaller.

Planned waterfront development in South Boston would be old by 2100, but a lot of the land there would be underwater, along with parts of existing landmarks, such as the Boston Fish Pier. The restaurants and pastry shops in the Italian North End would be spared, but parks and condos on the waterfront would be in trouble.

“The areas that would be affected are not only industrial sites and attractions, but places people live,” said Patrick Moscaritolo of the Greater Boston’s Convention & Visitors Bureau. “It has ramifications that are pretty drastic and pretty frightful.”

SAN FRANCISCO BAY

Rising waters would submerge some of the best of San Francisco Bay: Fisherman’s Wharf, baseball, software companies, even parts of the wine country.

The southern bay, Silicon Valley and the fertile San Joaquin-Sacramento River Delta would be hardest-hit. Also under water would be San Francisco’s famed Embarcadero waterfront, runways at both the San Francisco and Oakland airports, and even the Oakland A’s planned new stadium in Fremont.

The Redwood Shores campus of business software maker Oracle Inc., which now has an ornamental pond, would be sitting in one

Standing in Baylands, one of the last remaining wetlands in the area, Stanford University climatologist Stephen Schneider said, “this is a critical ecosystem and it’ll be gone.” His wife, biologist Terry Root, noted that the endangered bird, the California clapper rail, hiding in the wetlands is “going to be extinct … because of sea level rise.”