Panama Canal - Gatum Atlantic locks.

At Colón in Panama, South America. 2017

The left side is the entrance to the canal's first lock and the right side is the exit into The Atlantic (Caribbean Sea). Notice the queue of ships in the distance and follow the train tracks here, down the slope of the lock where other locomotives (Mules) await the next ship. When they have finished their tow at the end of these locks they return speedily along another parallel track to the beginning.