9 Extraordinary Underground Cities

Humans like to build cities that reach for the sky, but sometimes they also build downward. Whether for protection, or just because they can, we've created many cities beneath the Earth's crust - or dug deep into the rocky faces of mountains. Here are nine of the most awesome. » 1/01/14 11:31am 1/01/14 11:31am

The Best of io9's Science and History Stories in 2013

This year, io9 brought you in-depth explainer stories on topics ranging from physics and history, to cognitive science and the politics of teaching evolution in schools. Here are 23 of the most exciting ones which you may have missed. » 12/23/13 11:39am 12/23/13 11:39am

This crosswalk is the result of scientific testing

Here's a story about how a little coat of paint save thousands of lives (and probably many more). Before World War II, there weren't too many automobiles in Britain. But after the war, when cars started taking over the world, things started getting unacceptably fatal. Scientists had to invent a new kind of crosswalk. » 10/11/13 8:40am 10/11/13 8:40am

8 Ruined Cities That Remain a Mystery to This Day

The world is full of ruined cities, but some have such mysterious rises and falls that they haunt our imaginations. Even if we know who built them, certain aspects of the city may simply defy comprehension in the modern age. Here are 8 ancient cities that we may never fully understand. » 9/02/13 1:40pm 9/02/13 1:40pm