This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

Orthodox church partially financed by Tsar Nicolas II.

The only Bahá'í house of worship in North America and one of only a handful worldwide.

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

The stately remains of Llywelyn the Great's mighty fortress.

A hermit's tiny cell built into the cliffside that saved him in South Pembrokeshire.

The oldest continual pilgrimage site in Britain was supposedly created by a gruesome beheading.

A harem-inspired Moorish fantasy design in a Victorian-era Welsh castle.

The Stonehenge of Wales is one of the grandest neolithic dolmens still in existence.

A breathtaking flower tunnel bursts with beautiful golden blossoms.

This lonely cast-iron structure is the only wave-washed lighthouse of its kind left in all of Britain.

A real-life Professor Snape once taught in this Welsh university building, which students of course nicknamed “Hogwarts.”

The remains of a small medieval chapel mark the legendary birthplace of the patron saint of Wales.

A wildlife paradise, this island is one of the world’s most important habitats for burrow nesting seabirds.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

An artistic tribute to the famous singer, just around the corner from where he was born.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

A hidden treasure in London with a rich medieval history, and the resting place of many luminaries.

His "Lionheart" is entombed separately from the rest of his body.

An ancient ossuary in Rouen.

London's only public statue of the much-married monarch adorns the gate to St Bartholomew’s Hospital.