Urban Areas: Dense human habitation.

Derived from 2002-2003 MODIS satellite data at 1 km resolution: Schneider, A., M. A. Friedl, D. K. McIver, and C. E. Woodcock (2003) Mapping urban areas by fusing multiple sources of coarse resolution remotely sensed data. Photogrammetric Engineering and Remote Sensing, volume 69, pages 1377-1386. naturalearthdata.com

MapBox: Add a new layer to a slot

This example uses a new slot property to add a layer to a predetermined location in the Standard style. Set the preferred slot on the Layer object before adding it to your map and your layer will be appropriately placed in the Standard style's layer stack. Examples > Add a new layer to a slot