Civil War-era Fort designed to withstand invasion and attack, with tricky traps called "murder holes."

Civil War Fort on an island in the Boston Harbor.

Quite simply the largest tree in the world (by volume).

The "world's biggest dinosaur" once housed a creationist museum in its abdomen.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

The highest point in Washington state is a volcano covered in glaciers.

The mighty room where the poet spent most of her life is available to rent for an hour or two.

This picturesque abandoned home is rumored to be a spite house.

This waterfront museum in Maine is dedicated to the history of the smoked-herring trade.

This natural wonder is disappearing at an alarming rate.

The 32nd president's sprawling cottage sits on an island enclave jointly managed by the U.S. and Canada.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

This playground sculpture of an icon from the past is dedicated to the children of the future.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

Legends surround this jagged rock formation in the New Mexico desert.

The only road through the heart of Glacier National Park.

An old trolley bridge was converted into a breathtaking garden bursting with colorful flowers.

All that remains of this Massachusetts town, demolished in the name of progress, is a stone marker.

The hill that gave the Massachusett tribe, and later the state, its name.

A modest reminder of treacherous waters at the Golden Gate.

The unbelievably opulent home built for an infamous newspaperman.

Nancy Thompson's Home from "A Nightmare on Elm Street."

This quirky piece of naval artillery has been deafening Canadians for over a century.