Onlookers were fascinated and flummoxed when three human figures appeared in the New York City sky, zooming around buildings and bridges.

These 15 decorative and functional objects, from handkerchiefs to power strips, are inspired by skyscrapers and city streets.

This billboard house concept by design team Apostrophy's turns sky-high urban advertising space into livable multi-story abodes with amazing views.

These photos give us a glimpse of a nearly century-old abandoned theater above a grocery store in New York, in a building which is due to be demolished.

A huge inflatable red ball travels around the world, showing up in cities like Toronto and Abu Dhabi, squeezed into entryways and hovering above the street.

Brooklyn-based artist Dan Witz shocks passersby with ultra-realistic painted images of people trapped behind grates in urban buildings.

The city of Lisbon, Portugal got creative in the face of budget issues this year with an annual Christmas light display that's as festive as ever.

The abandoned metro tunnels beneath Antwerp turn into an underground architectural museum mimicking an archaeological site in this intriguing proposal.

Factoria Joven, a skate park and climbing wall in Spain, sets an example for urban youth centers worldwide with its bright and beautiful architecture.

These cool portraits combine more than one image to create fun, crazy illusions that you have to see to believe.