These sub-farmland caves are home to a majestic stalactite known as the "Crystal King."

The world's longest known cave system.

Three and a half miles of cliffs, rocky beaches, Gilded Age mansions and 40 Steps to nowhere in particular.

This elaborate towering structure was once famed for its revolutionary height.

A layered tribute to the work of mosaicist Isaiah Zagar.

The highway's southernmost spot is a beloved local attraction.

A monument celebrating the idea of reaching inaccessible places.

Millions of numbers carved in glass represent the tattoos forced upon victims.

An interesting decoration on this historic site, this weathervane comes with as many legends as it does questions.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

Mrs. Mallard and her brood are a beloved fixture in Boston Public Garden.

The massive machine creates cracking displays of indoor lightning.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

One of the oldest used bookstores in the U.S. has been selling antiquarian treasures since 1825.

A pair of black granite tails dive into a sea of grass in landlocked Vermont.

This large cemetery is known as the museum of granite sculptures.

This New England covered bridge is home to the tale of a jilted lover known to haunt the area.

This 38-drawer structure claims the superlative title, but it isn't the world's only giant filing cabinet.

The sweetest graveyard in the world is filled with headstones for dearly de-pinted ice cream flavors.

The somber sculptures commemorating Irish Famine on the river Liffey in Dublin.

Amidst the bustling streets of Dublin, there is a hushed garden that is dedicated to "All those who gave their lives in the cause of Irish Freedom."

These moss-covered medieval ruins tower atop the smallest of Ireland's Aran Islands.

Mortarless walls that stretch for miles are a lovely solution for creating grazing land in the harsh terrain of the Aran Islands.