Then American sewers have some serious problems. Sewers where I live are quite clean and you can see the grey cement walls. Perhaps they use some sort of cleansing material and flush it every so often, but I've never seen a sewer like that before. Not in any I've been in and not in any movie I've seen or TV show/documentary. Also the thing was huge if it really was a sewer and find it quite hard to believe unless it was shown on the news or TV or wikipedia or something. Nobody knows what it is and at that size aren't looking into what it is?