The old fortress is located right behind the modern art museum 'Mudam' and the Museum 'Dräi Eechelen' in the business district Kirchberg. From it, you have the most beautiful view on the old town of Luxemburg, located right across the valley. If the weather is nice, people go there with friends to enjoy a beer or just relax in the sunset.
The view is very very beautiful, it gives you a different appreciation of the location of the old town with the valley surrounding it. It also is a bit of a secret place, never crowded. It's great to go there in summer, bring friends and beers and sit there all afternoon until sunset.
Climb on the fortress and walk through the tunnels! From there, you can also follow the path down to Paffenthal, which is pretty!