It was cold. Damp. Musty. The air had a unique odor to it, familiar yet still slightly repungent. For most people, visiting a former waste water treatment plant isn't their idea of a vacation, but here we found ourselves, in the dark, walking through what used to be Prague's main facility for processing waste. Gross? A little. But, for two engineers who love industrial history, this was a pretty cool place to see. And since it's not in use any more, it smells quite a bit more pleasant than it's modern, still in use, counterparts. But still, that odor, it lingers.