Allowing humans and fish alike to migrate from freshwater to saltwater and back again.

Deep into the lower floors of Pike Place, find a date with fowl fate.

This grand old 80-foot sequoia towers above the buildings in the city’s retail center.

Residents of Fremont in Seattle have considered it the center of the universe since the 1970s.

Seattle's super-sized cowboy apparel once belonged to a themed gas station that wrangled in herds of tourists.

A rotting tree in the middle of Seattle doubles as an elaborately-controlled art piece.

The tech giant built three enormous glass orbs in Seattle so employees could work inside a rainforest greenhouse.

The first park built over a freeway is a brutalist masterwork.

A wall of chewing gum moonlights as collective art.

This former coal gasification plant found a curious second life as a popular public park.

A museum dedicated to the history and exploration of both popular music and science fiction.

A walk through the historic city center, under the streets of Seattle.

A giant Troll lurks under one of Seattle's oldest bridges.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

This 18th-century sundial was designed to calculate the date of Easter each year.

The remains of the medieval wall that once surrounded Paris with ties to the construction of the Louvre.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

There are many Byzantine-era churches still standing in Athens, but this is the only one with a 2,500-year-old column rising through its roof.

View the ancient remains of buildings and the ancient "River of Hades" before hopping on a train.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.