Roman Remains, Arles, France. One of the fascinating things about Arles is its Roman history, which is everywhere, from the amphitheater which still dominates its center, to the walls which still encircle its core, to the network of tunnels hidden underfoot.

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You see, for every city that the Romans conquered or otherwise established, they had a plan. And it was always the same plan: the forum goes here, the baths go here, the temple goes here, etc. This works pretty well when you've got a nice flat plain to work with, but the uneven terrain of Arles didn't fit well with this scheme.

Undaunted, the Romans simply filled in the low points, with an amazingly well-engineered series of stacked arched tunnels. Called a cryptoporticus, this underground gallery dates back to 1st century BC, and to this day remains sturdily serving its original function of leveling out the town.

In World War II the Germans occupied Arles, and the cryptoporticus found a new purpose --resistance fighters were hidden in these tunnels.

The lack of exposure to the elements has left these tunnels very well-preserved, and a walk through their quiet darkness is a form of time-travel (as well as being blissfully cool on a hot day).

This amazing site is included in the Arles Pass, a great value if you have enough time and energy to visit several of the nine attractions included.