Luxembourg City is built on a rocky plateau, which means the city stands on a flat-topped hill of stone. All around its edges the ground drops suddenly into steep, wooded valleys called the Pétrusse and the Alzette. Bridges called viaducts leap over these valleys so people can cross from one part of the city to another.
Below the old streets, there is a whole hidden world: a maze of tunnels and passages carved into the rock called the Bock Casemates. These passages are enormous - you could fit a double-decker bus inside some of them. Today they are open as a tourist attraction and children love exploring the cool, echoing corridors.
The oldest part of the city is called the Corniche, and it runs along the clifftop above the valley. People who live there have a view straight down to orange-roofed houses sitting snugly at the bottom, with trees and a river winding between them. It is one of the most famous views in all of Europe.
Every summer the city fills up with flowers in window boxes and the narrow lanes bustle with people from all over the world. Because Luxembourg is right in the middle of Europe, the city mixes French, German and its very own Luxembourgish language all at once.