Tony Webster/Flickr
If you ever plan to take a trip to Stockholm, Sweden's capital city, take note of the subways: they're works of art in and of themselves.
The stations are hewn into the bedrock in a way that makes them feel organic. At the same time, the layers of paint and murals add man-made, artistic touches. It's a fantastic juxtaposition between rugged and ultra-refined.
Here's a look at some of the city's amazing, cave-like subway stations: