Unfortunately, geography is against your friend there. These cities are all with the exception of Frankfurt in the Rhineland, and Frankfurt is in Hesse. Frederician sites and points of interest are in East Germany, in Berlin, Potsdam, the rest of Brandenburg. Rhinelanders, um, rather loathed the Prussians. By and large.
This being said, there's a lot of history in each of these places to be admired!
Trier: oldest Roman settlement still existing in Germany. Roman governors used to reside there. Also, hometown of Karl Marx. Has the Rheinisches Landesmuseum Trier with the greatest collection of Roman mosaics north of the Alps along wit the greatest Roman treasure. There's also a Marx museum and a big Chinese donated statue.
Frankfurt: a lot was destroyed and had to be rebuild after WWII. Museum wise, I'd say one must is the Goethe Museum - Goethe was born there, and not visiting is like going to Stratford and never visiting either of the two Shakespeare houses - which also offers a good exhibition on the time of Goethe's youth, which, of course, overlaps with Frederick's middle and old age. There's also a Jüdisches Museum - Frankfurt used to have one of the biggest Jewish communities in Germany - and a Archäologisches Museum worth visiting, although if your friend has already done Trier and is short of time, they might want to skip. To me, visiting the Paulskirche would also be a must, as this is where in 1848 there was the first attempt at a freely elected German Parliament and creating a constitution. This ended with the repression of the 1848 revolution and badly, but it's still a poignant place. There's a rotunda with a painting depicting all the 1848 parliamentarians, including Jacob Grimm (one of the two fairy tale gathering brothers Grimm).
Cologne: the cathedral, of course. Step out of the train station and into the cathedral, it's that close. The Römisch-Germanisches Museum is a must again for the Romans and ancient Germans, even if you've been in the Trier Museum, because it's one of the best archaelogical museums of Europe. The NS Dokumentationszentrum is the largest local museum devoted to documenting the crimes of the Third Reich in a German city.
Bonn: Beethovenhaus (birthplace of Beethoven) and Schumannhaus, devoted to these respective composers. The bungalow of the chancellors, i.e. where our heads of state resided before the capital moved to Berlin again post reunification. Noteworthy for being a normal size ordinary citizen bungalow, in intentional contrast to the Third Reich architectural megalomania. The Kunstmuseum Bonn, one of the best museums devoted to contemporary art.
Luxembourg: never having been there myself, have to pass.
Like I said: none of these cities are connected to Frederick unless very remotely (as in, young Goethe was a fan) - it's completely the wrong region of Germany for that, with a century old tradition of resenting Prussians that's only rivaled by Bavarians resenting them even more. (Frederick himself was popular as a character, mind.) He's never been in any of these places except en route to being somewhere else.
Re: Frederick for Americans?
This being said, there's a lot of history in each of these places to be admired!
Trier: oldest Roman settlement still existing in Germany. Roman governors used to reside there. Also, hometown of Karl Marx. Has the Rheinisches Landesmuseum Trier with the greatest collection of Roman mosaics north of the Alps along wit the greatest Roman treasure. There's also a Marx museum and a big Chinese donated statue.
Frankfurt: a lot was destroyed and had to be rebuild after WWII. Museum wise, I'd say one must is the Goethe Museum - Goethe was born there, and not visiting is like going to Stratford and never visiting either of the two Shakespeare houses - which also offers a good exhibition on the time of Goethe's youth, which, of course, overlaps with Frederick's middle and old age. There's also a Jüdisches Museum - Frankfurt used to have one of the biggest Jewish communities in Germany - and a Archäologisches Museum worth visiting, although if your friend has already done Trier and is short of time, they might want to skip. To me, visiting the Paulskirche would also be a must, as this is where in 1848 there was the first attempt at a freely elected German Parliament and creating a constitution. This ended with the repression of the 1848 revolution and badly, but it's still a poignant place. There's a rotunda with a painting depicting all the 1848 parliamentarians, including Jacob Grimm (one of the two fairy tale gathering brothers Grimm).
Cologne: the cathedral, of course. Step out of the train station and into the cathedral, it's that close. The Römisch-Germanisches Museum is a must again for the Romans and ancient Germans, even if you've been in the Trier Museum, because it's one of the best archaelogical museums of Europe. The NS Dokumentationszentrum is the largest local museum devoted to documenting the crimes of the Third Reich in a German city.
Bonn: Beethovenhaus (birthplace of Beethoven) and Schumannhaus, devoted to these respective composers. The bungalow of the chancellors, i.e. where our heads of state resided before the capital moved to Berlin again post reunification. Noteworthy for being a normal size ordinary citizen bungalow, in intentional contrast to the Third Reich architectural megalomania. The Kunstmuseum Bonn, one of the best museums devoted to contemporary art.
Luxembourg: never having been there myself, have to pass.
Like I said: none of these cities are connected to Frederick unless very remotely (as in, young Goethe was a fan) - it's completely the wrong region of Germany for that, with a century old tradition of resenting Prussians that's only rivaled by Bavarians resenting them even more. (Frederick himself was popular as a character, mind.) He's never been in any of these places except en route to being somewhere else.
I