The ruins of an 800-year-old monastery boasts the tallest round tower in Ireland.

After being destroyed by IRA sympathizers, the ruins of this stately Irish manor have sat vacant for decades.

The 19th-century pharmacy (now a used bookstore) was featured in James Joyce’s "Ulysses," and has changed very little to this day.

The world's toughest modern Christian pilgrimage leads directly to the gates of Hell.

A rocky Irish outcropping with a history of wealth, conflict, and ruin.

Once the longest bridge in Ireland, this rusting span sits abandoned and overrun by nature.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

Obelisks and stone pineapples in the Irish countryside.

An Iron Age fort on the edge of a seaside cliff offers a glimpse into an ancient, mystical world.

This ancient Irish religious site is covered in ancient carvings, many of which have barely aged.

The enchanting archway is the only surviving portal into Dublin's lost medieval wall.

An 80-year-old plane tree is devouring an iron bench at Ireland's oldest law school.

Ordinary art transforms to extraordinary thanks to locals' quirky sense of humor.

A French artist's vague warning hangs over Belleville.

An immersive projection art installation uses sound, scale, and light to take visitors inside classic works of art.

Architect Le Corbusier built his friend a cubist house to match his impressive collection of cubist art.

Despite being considered a thoroughly American sport, basketball's oldest surviving playing field is found in the basement of a Paris YMCA.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

The floorboard scrawling of a tragic madman is on public display outside a Paris hospital, much to the dismay of its opponents.

A popular shrine where the Blessed Virgin allegedly appeared in 1830, displaying a holy armchair and two incorruptible remains of Lady Saints.

This banal Parisian entranceway is not what it seems.

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.