This project uses OpenStreetMap to render the (present day) natural features and (if enabled as a setting) the current road network. Unfortunately, Brughmans,

This project uses OpenStreetMap to render the (present day) natural features and (if enabled as a setting) the current road network. Unfortunately, Brughmans, de Soto, and Pažout neglected to include the legally required attribution for this use of OpenStreetMap data (via Mapbox). This is a shame, because these kind of projects are great to show people that there is more than just Google Maps.