This is a good photo taken in the Gatun River valley area.  It shows fill already being dumped off the trestle in the distance.  This will be only a causeway through the Gatun Lake soon.  The photographer is standing on a hill that will become a island.  

Now you can see where all those stumps in the lake came from.  The jungle was not cleared when the lake was flooded but left to  eventually decompose.  The larger trees are still there under water.  There is a company in Panama today that is harvesting some of the big hardwood trees out of the lake.  The wood has been preserved all these years underwater.