This is personal, I love to walk around old castles and forts and that is why there are so many photos of this colossal fortress. It was once surrendered to the French, but that was before it was rebuilt to what it is today. The trip over the Rhine by cable car on a clear day is fantastic all by itself. It takes you to the large open field on the top of a ridge where in the distance you can see the low buildings that make up the museum entrance. Walk in that direction and you will notice a low wall with lots of domed window openings and long ago behind every one of them a cannon. Get closer to that low wall and you discover there are 3 floors of them with a steep drop into a large alley with more of those domed windows and slits on both walls for riflemen. Oh there is a small pillbox before you even get to the alley. Later you will discover that this is only the first such alley. Both alleys run from one side of the ridge to the other.
Thankfully you don't have to fight your way in. You are free to walk around at will and almost everywhere there is something interesting. The history of the site from well before Roman times is shown with relics and drawings. There is a model of a Roman Bridge typical of the one built by the legions of Julius Caesar to cross the Rhine. He had it built in 12 days to cross the river to subdue 2 German tribes. They united, he retreated and destroyed the bridge behind him.
There are exhibits of weapons before gunpowder like a crossbow on a pedestal mount. Several types of cannon and everyday items like a wine press and distilling system are exhibited. Inside where one would expect the enemy to concentrate their fire, the walls were very thick and the corridor is more like that of an underground mine.
The fort was also a palace at one time and some of the inner buildings reflect a less military stature. From both sides of the ridge the views are spectacular. On the land side you can see other small castles and the town below. On the river side, the view of Koblenz is gorgeous. On both sides the slant of the ridges are very, very steep.