Add custom 3D visualisations to a web or mobile map by using Mapbox fill-extrusion layer type and specifying the height and base height of a polygon feature.

For example, you can now easily render 3D buildings, or use the extrusion feature to represent other data (e.g. population density across your city's downtown) when used with data-driven styling and the recent addition of building heights to Mapbox Streets map style.

More info: https://www.mapbox.com/mapbox-gl-js/example/3d-buildings/, https://blog.mapbox.com/3d-features-in-mapbox-gl-js-e94734f12110