This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

The world's oldest bookshop still in operation.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

An ornate private entrance to the Vienna subway built specifically for the emperor.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

A patriotic medieval knight in driven-nail armor raised money for widows and orphans of WWI.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

Legends surround an ancient tree trunk riddled with nails for good luck.

Baroque celebration of the end of the Great Plague of Vienna.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The beautiful baroque library of the Hapsburg empire.

These gigantic skeletons tower over visitors and provide insight into the creatures that once ruled over Ireland.

This neon landmark has been posing this deadpan question to follicly-challenged Dubliners for over 50 years.

The chaotic studio of one of the 20th century's most important artists has been preserved down to the dust.

A statue in the center of Dublin dedicated to one of their favorite sons of rock & roll.

The modern birthplace of Irish freedom.

The Grand Lodge of Ireland is one of the oldest in the world, full of fantastical, elaborately themed rooms.

This courtly monument celebrates an influential comedian who turned taking the piss out of the powers-that-be into an art.

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

More than 5,000 artifacts donated by the people of the city, plus a room entirely devoted to the band U2.

The oldest public library in Ireland.