Nuraghi with Google maps
In short for the lowest zoomlevels (ranging from 1 to 9) the clustermarkers (really div elements) show the data for the provinces and the number of nuraghi, while at the intermediate level (up to 11) the clustermarkers show the data for single places with the number of nuraghi. The div elements have a background image (the icon) while the marker is transparant and contains the call to the infowindow with the data on the number of nuraghi and the province and place names. When zooming in to zoomlevel 12 and higher the markers are rendered individually, each indicating a nuraghe, also with it's own infowindow that shows the information on the nuraghe. In this way adding up to 6000 entries should not slow down the rendering of the page, and additional information to be displayed in the infowindow will not slow down the loading of the data too much. It even becomes quite nice to see the markers rendered at the higher zoomlevels and for the visitor it is even fun playing and clicking around.