One of a series of stereoscopic spherical views of the bridges in Philadelphia's Wissahickon Valley Park. This one shows the two bridges nearest the Wissahickon's confluence with the Schuylkill River:  the Ridge Avenue highway bridge, and the grand tall railroad bridge called the Wissahickon Creek Crosssing Viaduct.  The dam just visible upstream is technically not a bridge, though it can be crossed (illegally) on foot.