Bridge over ?

This picture was taken several years ago while driving around Costa Rica with a couple of surveying buddies. Being as we were employing the catch and release method of sampling the native cerveza one of them said:" Hey pullover when we get to the other side of this bridge." So we did. A minute later the two of us in the car hear:"Hey comeer look at this" So we did. And this is what we saw. We had never seen a bridge like this before, we figured the plans must have been upside down when they were building it.