Large museum with a great collection of ancient art from the Roman Rhineland: Bonn itself of course, but also Cologne, Xanten, and so on. Among the Roman objects is the famous cenotaph of Marcus Caelius. Even more famous (but not Roman) is the skeleton of the first Neanderthaler, which was discovered in a nearby valley.
There are 44 items in Bonn, Rheinisches Landesmuseum:
Coin by Domitian, announcing the conquest of Germania
Hambach-Niederzier, Gold treasure
Model of the Eburonian settlement at Hambach-Niederzier, which was abandoned after the mid-first century BCE.