Cesium is an open-source JavaScript library for creating 3D and 2D web maps.  It uses WebGL for hardware-accelerated graphics.  Version 1.0 includes support for worldwide high-resolution terrain; global imagery from standards such as WMS, OpenStreetMap, Bing Maps, and ArcGIS MapServer; vector data from GeoJSON and TopoJSON; 3D models using glTF; and a large geometry library.