in 1984 4,466 people lived in 375 houses, whereas a 1995 census showed that the citadel had only 1,631 inhabitants living in 247 houses. Until the opening-up of the main north–south thoroughfare, the streets on the citadel mound radiated outward from the southern gate like the branches of a tree. Streets were between wide and ranged in length from for major alleyways to for cul-de-sacs. The perimeter wall of the citadel is not a continuous fortification wall, but consists of the façades of approximately 100 houses that have been built against each other. Because they have been built on or near the steep slope of the citadel mound, many of these façades were strengthened by buttresses to prevent their collapse or subsidence. There were circa 30 city-palaces; most of them located along the perimeter of the citadel. The oldest surviving house that can be securely dated through an inscription was built in 1893. The oldest houses can be found on the southeastern side of the mound, whereas houses on the northern perimeter date to the 1930s–1940s. Before the introduction of modern building techniques, most houses on the citadel were built around a courtyard. A raised arcade overlooking the courtyard, a flat roof and a bent-access entrance to prevent views of the courtyard and the interior of the house were characteristic elements of the houses on the citadel. Research and restoration In 2006 and 2007, a team from the University of West Bohemia, together with Salahaddin University in Arbil, carried out an extensive survey and evaluation of the entire citadel. As part of this project, geodetic measurements of the citadel were taken and these were combined with satellite imagery, regular photographic imagery and aerial photographs to create a map and digital 3D model of the citadel mound and the houses on top of it. Geophysical prospection was carried out in some areas of the citadel to detect traces of older architecture buried under the present houses. Archaeological investigations included an archaeological survey on the western slope of the citadel mound, and the excavation of a small test trench in the eastern part of the citadel. in 2012, the Higher Committee for the Maintenance and Rehabilitation of the Erbil Citadel decided to identify seven areas inside the Citadel to conduct excavations, and to search for the remains of the wall and the historical fortifications of the citadel, the commission chose point E