This is the backyard of the Pedersen residence and what you are looking at is the station of the Niles Monorail.
A monorail is a metro or railroad with a track consisting of a single rail (actually a beam), as opposed to the traditional track with two parallel rails. Monorail vehicles are wider than the beam they run on.
The suspended monorail ("Schwebebahn") of Wuppertal (Germany) dates from 1901 and is still in operation. The tracks are 8 m above the streets resp. 12 m above the Wupper river.
In 1950, the famous German circus Althoff had the young elephant Tuffi take the Schwebebahn as a marketing gag. Tuffi broke through a window and jumped into the Wupper, suffering only minor injuries.
The Schwebebahn is reported to be the world's safest transport system. The only severe accident happened on April 12, 1999, when 5 people died and 46 were injured after a train derailed and crashed into the Wupper. The accident was caused by a construction worker's leaving a tool on the track.