The world of the ancient Celtic civilization explained through a bewitching 11 acre garden.

A moody and picturesque riverside ruin overgrown with vegetation.

A six-ton wedding present for the King of the Scots.

A sweet symbol marks the place where torturous executions were once carried out.

The 16th-century church has the only stained glass windows that survived the Scottish Reformation intact.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

360° views of the city plus five floors of optical illusions and hands-on science.

Every birth, death, and marriage is recorded in these color-coded leather-bound books.

Small museum dedicated to the founder of electromagnetic theory.

These ruins witnessed the final gathering of the failed Jacobite Rebellion.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

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.

A 400-year-old church covered floor to ceiling in ex-voto offerings from the faithful.

The site of the first medieval crusade that pitted Christians against Christians.

This 1920s Dutch barge is now a floating bookstore.

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

Tables of secondhand books fill the inner courtyard of this 17th-century stock exchange.

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."

The comedy and tragedy of Oscar Wilde is preserved in a Dublin park, captured in a sculpture of colorful stone.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The oldest public library in Ireland.

A particularly disconcerting tribute to Irish martyrs.

Dublin's "Dead Zoo" serves as a window to Victorian museum design.