Surrounded by low rise buildings and partially converted into an auto body shop, this marble archway is the only vestige of a forgotten Manhattan estate.

A crumbling hospital from the 1850s on Roosevelt Island.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

Site of the first pathological and bacteriological research facility in the United States.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

The oldest continuously inhabited street in America.

The origins of midtown Manhattan's anachronistic wooden farmhouse remain a mystery.

A small part of lower Manhattan is actually made from a bit of England.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

One of only two commuter aerial tramways in the United States.

A small peaceful park and waterfall tucked amid the urban grind of Midtown Manhattan.

Peek through the gates at this oasis from the city, full of Old English charm.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

Manhattan and the Bronx have been playing tug-of-war over this former island neighborhood for more than a century.

A pride of the state, this working museum crafts pottery mosaics in the style of Pennsylvania's earliest European settlers.

Holding multiple historical boats and an entire 19th century village, this New England attraction is the largest maritime museum in the world.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

This Wall Street bar was once a hub of revolutionary activity where Washington famously bid farewell to his troops.

The home of the first American-born saint is one of the only curved buildings in New York.

Built hundreds of years ago this downtown iron barrier once protected a much despised king.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

A discreet little stairway on St. Nicholas Avenue leads to a quaint and unexpected cobblestone street of 19th century wooden rowhouses.