Some scholars have suggested that the earliest manifestation of the Kura-Araxes phenomenon should be dated at least to the last quarter of the 5th millennium BC. This is based on the recent data from Ovçular Tepesi, a Late Chalcolithic settlement located in Nakhchivan by the Arpaçay river. Rather quickly, elements of Kura–Araxes culture started to proceed westward to the Erzurum plain, southwest to Cilicia, and to the southeast into the area of Lake Van, and below the Urmia basin in Iran, such as to Godin Tepe. Finally, it proceeded into the present-day Syria (Amuq valley), and as far as Palestine. Its territory corresponds to large parts of modern Armenia, Azerbaijan, Chechnya, Dagestan, Georgia, Ingushetia, North Ossetia, and parts of Iran and Turkey. At Sos Hoyuk, in Erzurum Province, Turkey, early forms of Kura-Araxes pottery were found in association with local ceramics as early as 3500-3300 BC. During the Early Bronze Age in 3000-2200 BC, this settlement was part of the Kura-Araxes phenomenon. At Arslantepe, Turkey, around 3000 BCE, there was widespread burning and destruction, after which Kura-Araxes pottery appeared in the area. According to Geoffrey Summers, the movement of Kura-Araxes peoples into Iran and the Van region, which he interprets as quite sudden, started shortly before 3000 BC, and may have been prompted by the 'Late Uruk Collapse' (end of the Uruk period), taking place at the end of Uruk IV phase c. 3100 BC. Archaeological evidence of inhabitants of the Kura–Araxes culture showed that ancient settlements were found along the Hrazdan river, as shown by drawings at a mountainous area in a cave nearby. Structures in settlements have not revealed much differentiation, nor was there much difference in size or character between settlements, facts that suggest they probably had a poorly developed social hierarchy for a significant stretch of their history. Some, but not all, settlements were surrounded by stone walls. They built mud-brick houses, originally round, but later developing into subrectangular designs with structures of just one or two rooms, multiple rooms centered around an open space, or rectilinear designs. At some point the culture's settlements and burial grounds expanded out of lowland river valleys and into highland areas.