www.dw.de/hidden-stonehenge-revealed/g-17914078 8:00 am cst 11.09.2014 Author Kate Müser www.dw.de/ The subterranean images revealed prehistoric pits, hundreds of burial mounds, and settlements from the Bronze Age, Iron Age and Roman times. The data gives researchers new insights on the surrounding area, spanning a time frame of over 11,000 years. The field work took 120 days, spread over four years.