Beware of cobbles
Cobbles! I think I never encountered more extensive stretches of real ancient gnarly medieval cobble stones like in the old cities of the eastern Harz region. Namely Quedlinburg which really surprised me with the really widestretched historic part of old buildings, alleys and places. Nearly all paved by such cobbles. These and the ones of the neighbour town Blankenburg would swallow my not that small 28 mm tires easily between them. So if you ever want to do extensive city exploring in those towns some big volume tires wouldn’t be the worst of ideas.