The site where a plot to assassinate Hitler was planned—and its conspirators were executed—is now a powerful memorial to the German resistance during World War II.

This TV tower once secretly housed a GDR intelligence team.

The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

Read between the lines of the subway map to find the hidden abandoned Civil War fort.

An iconic and controversial ancient Iberian funerary urn with a hauntingly penetrating gaze.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."