It's actually the Rakotzbrücke (Rakotz Bridge, also called Devil's Bridge) in the Azalea and Rhododendron Park in the district of Kromlau in Goblenz, Germany. It was built as part of the park development and completed in the 1860s.
Here's what it looks like in Google Maps.
It's also apparent it isn't as huge as it looks in the first picture. It's a semicircular arch, and the stream is about 70 feet wide, so the arch is about 35 feet high.