Old ruins seem to me to be a good candidate for black and white. These ruins were on a hill top over looking the Rhine river in Germany.
There is a stretch of river along the northern Rhine that has over 25 old ruins. Some have been restored, most have not. Many of these castles fell to Louis XIV in the 1670s when France annexed parts of the German border.
Using monochrome here gives a sense of a dark dreary sky and shadows where it was actually a bright and sunny day.
Due to a prior commitment all I can do are 3 Monochrome days. Not only has this been fun but it has reminded me of the 35mm days and how B&W can change the entire direction of a photo.
Thanks for the push to monochrome John Etheridge.