The huge (nearly 2.5 kilometers long) earthen Gatún Dam was built to create Lago Gatún  (Gatún Lake), a vital part of the Panama Canal . It was the largest such structure in the world when the canal opened in 1914.
The dam controls the flow of the mighty Río Chagres , a major obstacle to canal builders, and supplies electricity used at the locks and the surrounding communities. It’s an awesome sight when the spillway is opened and the water comes roaring out. A small bridge runs right by the spillway, behind which there’s a good view of the canal.
To get to Gatún Dam, cross over the swing bridge that spans the north end of Gatún Locks . The wait can be up to half an hour if a ship is transiting, but the bridge provides a fascinating fish’s-eye view of the locks since one actually drives through a lock chamber. Take the first left after the bridge and head up the road for about two kilometers.
Note: There is now a free car ferry across the channel that runs 5 A.M.–9 P.M. daily. But the wait can be as long as an hour, depending on ship traffic, for the three-minute ride. For safety reasons you’re not even allowed out of the car. The ferry is meant primarily for heavy equipment and trucks too big for the swing bridge, which is far more interesting and comparatively speedy.