Looks good with respect to using auto. One question inline, might be a missing reference.
https://codereview.appspot.com/583750043/diff/557770050/lily/skyline.cc File lily/skyline.cc (right): https://codereview.appspot.com/583750043/diff/557770050/lily/skyline.cc#newcode584 lily/skyline.cc:584: for (auto const b : buildings_) I think this will do a copy of every building. Did you actually want to use for (auto const &b : buildings_) ? https://codereview.appspot.com/583750043/
