It's not pretty, but this hole in the ground is the sign of an expert drug smuggler. It's part of a 180 metre tunnel under the California-Mexico border and it connects a warehouse in Tijuana with one in San Diego.
It seems that while such drug smuggling tunnels aren't terribly uncommon—about 125 have been discovered since the 1990s—it is tough to actually find them. There are special U.S. border tunnel task forces dedicated to tracking them down and they use the latest ground-penetrating technology as well as robot scouts to search for and through them.
There aren't too many details about the recently discovered tunnel in the photo above, but it's definitely housed a reasonably high-tech operation considering that it contained proper rail, lighting and ventilation systems as well as 30 tons of marijuana. [CNN]