Passerelle (Old Bridge), Luxembourg (must see)

The Passerelle, also known as the Luxembourg Viaduct, runs from the south into the city centre, Ville Haute, carrying road traffic across the Pétrusse valley and connecting Avenue de la Gare to Boulevard Franklin Delano Roosevelt. It is 290 m long, with 24 arches, and 45 m above the valley floor.

It is also known as the Old Bridge by people from Luxembourg City. The 'new bridge' in this comparison is the Adolphe Bridge, which was built between 1900 and 1903.

The Passerelle was built between 1859 and 1861 to connect the city centre with Luxembourg's new railway station, which was located away from the city centre so as to not detract from the defensive capabilities of the city's fortress. It was conceived by the engineers Achille N. Grenier and Auguste Letellier, and built by the British company Waring Brothers.

Why You Should Visit:
For starters, you can explore it for hours without spending a dime. In addition, the views there are nothing short of glorious, especially when the weather is on your side.
It helps with orientation so that you can choose which direction to explore later, and the bridge's features and symmetry are lovely, too.

Tip:
Wear some decent walking shoes and if you have moderate mobility issues some hiking sticks are to be considered.