If cities are the hearts of our civilization, then the metro systems are the main arteries. This week, PicsArtists give us a glimpse of life below the street level. Through their lenses, we can see the underground network of metro lines and the constant flow of inhabitants that use them to travel between critical city centers.

The following gallery depicts metro systems across the world. Leave a comment to share your thoughts.

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures

metro pictures