Very steep stairs, so when arriving at the top you’ll be out of breath (don’t forget to take a bottle of water with you). But really worth doing so when visiting Liège. It is really a must see. The view is beautiful and you’ll be proud of your own accomplishment!

Information
Montagne de Bueren
4000 Liège
Belgium
https://en.wikipedia.org/wiki/Montagne_de_Bueren

Visited July 2017. You can find my review about Montagne de Bueren also on TripAdvisor.