<P> A memorial at the site, the National September 11 Memorial & Museum, was opened to the public on September 11, 2011 . A permanent museum later opened at the site on March 21, 2014 . Upon its completion in 2014, the new One World Trade Center became the tallest skyscraper in the Western Hemisphere, at 1,776 feet (541 m). Other skyscrapers are under construction at the site . </P> <P> On October 29 and 30, 2012, Hurricane Sandy caused extensive destruction of the state's shorelines, ravaging portions of New York City and Long Island with record - high storm surge, with severe flooding and high winds causing power outages for hundreds of thousands of New Yorkers, and leading to gasoline shortages and disruption of mass transit systems . The storm and its profound effects have prompted the discussion of constructing seawalls and other coastal barriers around the shorelines of New York City and Long Island to minimize the risk from another such future event . This is considered highly probable due to global warming and rise in sea levels . </P> <P> New York covers 54,555 square miles (141,300 km) and ranks as the 27th largest state by size . The highest elevation in New York is Mount Marcy in the Adirondacks, at 5,344 feet (1,629 meters) above sea level; while the state's lowest point is at sea level, on the Atlantic Ocean . </P> <P> In contrast with New York City's urban landscape, the vast majority of the state's geographic area is dominated by meadows, forests, rivers, farms, mountains, and lakes . Most of the southern part of the state rests on the Allegheny Plateau, which extends from the southeastern United States to the Catskill Mountains; the section in New York State is known as the Southern Tier . The rugged Adirondack Mountains, with vast tracts of wilderness, lie west of the Lake Champlain Valley . The Great Appalachian Valley dominates eastern New York and contains the Lake Champlain Valley as its northern half and the Hudson Valley as its southern half within the state . The Tug Hill region arises as a cuesta east of Lake Ontario . </P>

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