Have a play!

Hover or single-tap clusters to see the marker population "foot-print" and the names of the underlying subregions. Click or double-tap on the clusters to zoom in. As you zoom in deeper, the active region level moves from country to state to city and the region tool tip (or popup) reflects this.
Zoom out using the minus sign in the upper left corner. Or use the "pinch action" on a touchpad or mobile.
You can also pan the map. Go full screen by clicking the square.