One chilly autumn morning, I wandered through the medieval alleys of the historic old town of Monschau, Germany. Monschau nestles in the hills of Eifel, where the Rur River runs through it.

The cobblestone streets of Monschau are decked with half-timbered structures with horizontal weatherboard walls and locally quarried slates.

To illustrate an example, the Burgau 1, a charming half-timbered house at the bank of a bridge, has a white weatherboard wall. The upper floor and the attic have slates.