As we continued to float the Rhine River thru Germany for several days, we had the privilege of visiting some ancient castles, quaint villages, and historical architectural wonders. I guess my favorite was the Cologne Cathedral in Germany. This fascinating Gothic structure was built over a span of 600 years.. Between 1248 and 1850. In 1880, it was the largest cathedral in the world …and during WWII, it was the only building of significance that was not bombed. It appears mostly black even though it’s made of sandstone… This is because the diesel trains running nearby for hundreds of years have put out black smoke which seeps into the stone.