Strange all-white road in city

[thetacola]

I've just started a new game, and came across a tile that's completely white right next to city hall. Clicking on it says that it's a cobblestone street, and hovering over it shows that it's sloped. Is it safe to assume it's a bug? If not, is there anything special about the pure white road? I've attached a screenshot and the save to show what I mean