They are often near giant's grave or the other megalithic monuments. The French Comte de Caylus was the first to describe the Carnac stones. Pierre Jean-Baptiste Legrand d'Aussy introduced the terms "menhir" and "dolmen", both taken from the Breton language, into antiquarian terminology. He mistakenly interpreted megaliths as Gallic tombs. In Britain, the antiquarians Aubrey and Stukeley conducted early research into megaliths. In 1805, Jacques Cambry published a book called "Monuments celtiques, ou recherches sur le culte des Pierres, précédées d'une notice sur les Celtes et sur les Druides, et suivies d'Etymologie celtiques", where he proposed a Celtic stone cult. This unproven connection between druids and megaliths has haunted the public imagination ever since. In Belgium, there are the Wéris megaliths at Wéris, a little town situated in the Ardennes. In the Netherlands, megalithic structures can be found in the northeast of the country, mostly in the province of Drenthe. Knowth is a passage grave of the Brú na Bóinne neolithic complex in Ireland, dating from c. 3500–3000 BC. It contains more than a third of the total number of examples of megalithic art in all Europe, with over 200 decorated stones found during excavations. Nabta Playa at the southwest corner of the western Egyptian desert was once a large lake in the Nubian Desert, located 500 miles south of modern-day Cairo. By the 5th millennium BC, the peoples in Nabta Playa had fashioned an astronomical device that accurately marks the summer solstice. Findings indicate that the region was occupied only seasonally, likely only in the summer when the local lake filled with water for grazing cattle. There are other megalithic stone circles in the southwestern desert. Namoratunga, a group of megaliths dated 300 BC, was used by Cushitic-speaking people as an alignment with star systems tuned to a lunar calendar of 354 days. This discovery was made by B. N. Lynch and L. H. Robins of Michigan State University. Additionally, Tiya in central Ethiopia has a number old megaliths. Some of these ancient structures feature engravings, and the area is a World Heritage Site.