Here's something I don't think I've ever told anyone: I have this weird fascination with the marks and dates that I often see placed in the concrete of bridges and overpasses. I always notice them when I'm driving on a bridge or overpass and look for them when I don't see one in an obvious place. I'm no civil engineer though, so I don't have a clue as to their significance. Most of them appear to be the date the bridge was built - or maybe the date that the concrete pieces were poured. But some have additional information and I have thus far been unable to get Professor Google to educate me. Anyone care to enlighten me? This is the marker under the overpass near the Jefferson Memorial at the Tidal Basin. I think it's beautiful and one of the most interesting ones I've ever seen. Is it odd that I think this is beautiful? Don't answer that.