The remains of a ruined mansion memorialize the 1906 earthquake.

San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

Built in 1547, these ruins lie on a rocky promontory in Ballintoy jutting into the wild ocean waters below.

A proud bronze billy stands as an eternal symbol of Ireland's oldest festival, where a goat is made king.

This statue celebrating everyday life in Dublin has a few unsavory nicknames.

A mysterious plaque to the even more mysterious "Fr. Pat Noise," killed in "suspicious circumstances."

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

Dublin's most modern, visually spectacular bridge is modeled after Ireland's national emblem.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

This modest plaza in Moneygall, Ireland has cashed in on its distant connection to the U.S. president.

Northern Ireland's Brobdingnagian stepping stones.

The ancient tomb acts as a calendar that keeps perfect time.

This Neolithic passage tomb forms part of a World Heritage Site.

A boulder in the Churchyard of Down Cathedral marks the legendary burial place of "The Apostle of Ireland."

The historic home still shows the scars from a little run-in with the British in 1813.

Designed to commemorate the founding of the first settlement in Delaware.

One of Ireland's most infamous prisons for rebels including men, women and children.

A surprising, but overlooked example of geology in the middle of the nation’s capital.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

Visitors to Salt Springs State Park are encouraged to literally put their two cents in Penny Rock.

This small hilltop church weaves the urban history of Washington, D.C. with the national history of the United States.