landscape investigation was conducted in April 2009. A shallow mound, rising to about was identified between stones 54 (inner circle) and 10 (outer circle), clearly separated from the natural slope. It has not been dated but speculation that it represents careless backfilling following earlier excavations seems disproved by its representation in eighteenth- and nineteenth-century illustrations. There is some evidence that, as an uncommon geological feature, it could have been deliberately incorporated into the monument at the outset. A circular, shallow bank, little more than high, was found between the Y and Z hole circles, with a further bank lying inside the "Z" circle. These are interpreted as the spread of spoil from the original Y and Z holes, or more speculatively as hedge banks from vegetation deliberately planted to screen the activities within. In 2010, the Stonehenge Hidden Landscape Project discovered a "henge-like" monument less than away from the main site. This new hengiform monument was subsequently revealed to be located "at the site of Amesbury 50", a round barrow in the Cursus Barrows group. In November 2011, archaeologists from University of Birmingham announced the discovery of evidence of two huge pits positioned within the Stonehenge Cursus pathway, aligned in celestial position towards midsummer sunrise and sunset when viewed from the Heel Stone. The new discovery was made as part of the Stonehenge Hidden Landscape Project which began in the summer of 2010. The project uses non-invasive geophysical imaging technique to reveal and visually recreate the landscape. According to team leader Vince Gaffney, this discovery may provide a direct link between the rituals and astronomical events to activities within the Cursus at Stonehenge. In December 2011, geologists from University of Leicester and the National Museum of Wales announced the discovery of the source of some of the rhyolite fragments found in the Stonehenge debitage. These fragments do not seem to match any of the standing stones or bluestone stumps. The researchers have identified the source as a long rock outcrop called Craig Rhos-y-felin (), near Pont Saeson in north Pembrokeshire, located from Stonehenge. In 2014, the University of Birmingham announced findings including evidence of adjacent stone and wooden structures and burial mounds near Durrington, overlooked previously, that may date as far back as 4000 BC. An area extending to was studied to a depth of three metres with ground-penetrating radar equipment. As many as seventeen new monuments, revealed nearby, may