The Grandfey Viaduct in Fribourg is considered as an extraordinary feat of engineering. It was built in 1925-1927 out of concrete to support the arrival of electric trains and increasing speed at which they traveled. It measures 383m long and 82m high. Hundreds of walkers and bikers cross it via the footbridge every day. You can enjoy the views of the Sarine valley and feel the vibrations when the trains pass overhead.
https://goo.gl/maps/nsxGkgm6FhkBhihL9
https://www.fribourgtourisme.ch/en/P21375/grandfey-viaduc