Koblenz's Militarmuseum is a specialist stop for travellers interested in military engineering, equipment, and the city's long strategic position at the Rhine and Moselle. It sits outside the romantic riverfront image of Koblenz, but that contrast is part of the point.
Go if you already have an appetite for military history after Ehrenbreitstein Fortress or the river fortifications. Casual visitors may prefer the old town and cable car, but the museum adds a harder-edged layer to a city shaped by armies as much as by wine and river trade.