An underground city of salt.

Real bones which are said to have belonged to a Polish dragon.

What was once thought to be a wellspring of unicorn bones is actually just a prehistoric burial site.

America's most famous piece of self-built architecture.

A remarkably intact castle that once was the largest in Ireland.

A natural arch carved by a river gave its name to the so-called "Cave of Forgotten Dreams."

A museum dedicated to a secret military hospital hidden beneath a castle in Budapest.

Goethe's "Faust" was inspired by these rock formations known as the "Devil's Pulpit" and "Witches' Altar."

One-layer pyramid in Indiana.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

Perhaps the most unique of any Frank Gehry design for one simple reason: Gehry himself actually lives here.

In a city filled with Frank Gehry buildings, one stands out as one of the architect's weirder works.

The legendary building that needed ghostly approval before being built.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

The Sun King's military models, saved from the Louvre.

The crown jewel of the Queens Museum is a nearly 10,000-square-foot architectural model of the city originally built for the 1964 World's Fair.

One of the world's largest model railroads is a mind-boggling achievement.

A 400-square foot model of historic Quebec is the playing field for a state of the art light and sound show.

Back in the tiny USSR.

A swing to dangle you off the very edge.

A steam powered train that runs on city streets.

Model Trains and Much More in Hamburg.

A surrealist timepiece by the artist of melting clocks.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.