Site points are displayed if the map is zoomed in about halfway or greater. All sites in the DAAHL database are shown on the map irrespective of time period. To see sites by time period, press the "Archaeological Periods" link in the link bar. You can turn the PEF maps off by clicking one of the other buttons in the upper right corner of the map. Press the PEF Maps button on the map to turn the map layer back on.