Sagalassos was situated in the ancient region of Pisidia, named after its inhabitants, the Pisidians, an ethnic group descendent from the Indo-European Luwians. The ancient region of Pisidia corresponds with the present-day Lake District in the Turkish provinces of Burdur, Isparta and Antalya. Being part of the western Taurus, typical features of the Pisdian landscape are mountainous terrain, forested hills, valleys with river streams, and large plains with lakes.

The earliest indications of human activity in the area are lithic artefacts that could be dated back to the Middle Palaeolithic(150,000–45,000 BP), based on typological Levallois reduction traits. Despite these occasional finds, the prehistory of the Burdur area is mainly known from small, late prehistoric mound sites in the plains, such as Hacılar and Kuruçay Höyük, and short-lived Chalcolithic-Bronze Age settlements out in the open within their vicinity. However, clear evidence of human activity preceding 6500 BCE is scarce.

All known sites from Late Neolithic and Early Chalcolithic times  (6500-5500 BCE) were located in the valleys, with a clear preference for locations near fresh water sources, as well as fertile land, suggesting these locations were specifically cho­sen for agricultural purposes. It has been argued, that contemporary subsistence strategies of settlements in the Burdur Plain were characterised by a mixed farming tradition of plant cultivation and animal husbandry. After the Middle Chalcolithic (5300-4300 BCE), no direct evidence of human activity could be found in the Burdur Plain for a period of 1500 years. More is known from the Late Chalcolithic and Early Bronze Age periods (4200-2000 BCE), revealing the development of a dense settlement pattern.

The first clear indications in the area of human impact on the landscape can observed from 800 BCE onwards. Unfortunately we do not have a direct spatial association between archaeological and environmental data at this point, which rules out the possibility of directly relating the observed changes in the palynological record to the settlements known from the archaeological record.

At Sagalassos and in its immediate hinterland, virtually no traces of occupation in this period of time have been attested. Recent material studies identified two sherds dateable to the Iron Age period(possibly 7th-6th century BCE), whereas only a single black-on-red pottery sherd, dated to the 8th-6th centuries BCE, was found in the suburban surveys conducted throughout the central parts of the Ağlasun valley. In 546 BCE, the Lydian state was conquered by the Persians, led by the Achaemenid dynasty. The Achaemenid empire extended from Anatolia and Egypt throughout Western and Central Asia up until North India.

The first traces of occupation at Sagalassos can be dated back to late Achaemenid times (late 5th century BCE), however direct sociocultural impact of the Achaemenid administration on local configurations has been downplayed in recent archaeological research. At the same time of community formation at Sagalassos, traces of habitation can be found in other places throughout the Ağlasun valley. Most notably at a village located on a plateau overlooking the valley, situated about 1.8km to the southwest of Sagalassos, at a site called Düzen Tepe, as well as a number of farms spread throughout the valley.

In 334 BCE, the Macedonian king Alexander III (later named the Great) conquered the Achaemenid Empire. It was accounted by the Roman historian Arrian how Alexander in 333 BCE, took Sagalassos by storm after breaking local resistance on a steep conical hill south of the settlement. The settlement was described as ’not a small city’ at the time, however, as far as the archaeological record shows, it was probably no more than a village.

As a result of Alexander’s conquest, the area of Sagalassos and Pisidia became part of the Hellenistic world. It was ruled by a series of successive dynasties after Alexander’s death, respectively the Antigonids (321-281 BCE), the Seleucids (281-188 BCE), and the Attalids (188-133 BCE). During this period, communities in the geographic area of Pisidia gradually converged into larger territories associated with a number of urban centres, such as at Termessos, Selge and Sagalassos. At Sagalassos, the territory was extended to include the fertile Burdur plain in the early 2nd century BCE at the latest, possibly as a result of Seleucid policies or stimuli. A lot of Hellenistic settlements in the area were either fortified or located at elevated positions within the landscape, suggesting a continued concern for safety rather than agricultural potential. The extent of the impact of the incorporation of Pisidia in the Hellenistic kingdoms is an ongoing topic of current debates.

After the death of Attalos III in 133 BCE, the Attalid possessions in Anatolia were bequeathed to the Romans, whom incorporated most of the Attalid kingdom into the provincia Asia in 129 BCE. The Romans did not assert their dominance in Anatolia, until they fought and eventually defeated both Mithridates VI of Pontus, and the Cilician pirates during the first half of the 1st c. BCE. Western Anatolia was reorganised into provinces and client kingdoms in 63 BCE. After several eventful decades of conflict, Pisidia came under the rule of Amyntas of Galatia in 36 BCE. After his death in 25 BCE, Pisidia was incorporated in the Roman province of Galatia by the Roman emperor Augustus.

During the Roman Imperial period, increased construction of public buildings markedly changed the physical outlook of Sagalassos and many other cities. While mass production of pottery had already been initiated at Sagalassos in Late Hellenistic times, local potters started to produce a new type of fine Roman-style tablewares during the reign of Augustus, the so-called Sagalassos Red Slip Ware (SRSW), which continued until the 7th century CE.

Pottery production chiefly took place in the eastern part of town, originally called the Potter’s Quarter by us, but these days more generally denoted as the Eastern Suburbiumbecause of the presence of – besides pottery production – a wide range of artisanal activities, funerary activities, habitation and waste disposal. The community at Sagalassos – both elite and non-elite – made good use of the opportunities offered by the Roman Empire, and the city quickly became the first city of Pisidia.

Urban expansion and building activities continued well until the reign of Nero. It again reached new heights under the reign of Hadrian when a veritable ‘building boom’ ensued, including the Neon library, the Hadrianic nymphaeum, the Temple of Apollo Klarios and most notably the massive Roman Baths. Under the rule of Marcus Aurelius, the Baths were completed, as well as the Macellum situated between the Lower and Upper Agora. It is possible that the construction of the impressive theatre was initiated at this time as well. The elaboration of the urban infrastructure of Sagalassos would continue well into the 3rd century CE. In the early 4th century CE, the administration of the Roman Empire was re-organized and Sagalassos lost its leading role in the area to Pisidian Antioch. Still, this did not noticeably hinder the continued urban development and maintenance of the town

Between the middle of the 5th and the 6th century CE, amongst other buildings, eight churches were raised within the city and its periphery. Existing urban structures and features remained in use and well maintained, including the Baths complex, the city squares, porticoes and streets. From the late 6th century onwards, Sagalassos gradually attained a less urban character, as many public spaces and buildings became subdivided in several smaller units. This process of encroachment can be seen as indicative for the transformation of the urban fabric at the time.

By the end of the 6th century CE, the typical SRSW pottery was no longer produced in the city’s Eastern Suburbium, but possibly relocated to the surrounding countryside. A devastating earthquake in the 7th century CE proved to be the deathblow for many of the public buildings, to such an extent that this was previously thought to have ushered in the end of habitation at Sagalassos. More recently, however, it has been realized that the settlement remained occupied until the 13thcentury CE. Several attempts to maintain elements of the urban fabric, such as repairs of walls and other interior elements of the basilica at the former bouleuterion, and a defensive wall built across the southern part of the collonaded street, can be observed. The community seems to have been relocated upon a kastron on the plateau of the partially dismantled sanctuary of Antoninus Pius.

Ecclesiastical sources show that Sagalassos remained a bishopric of the province of Pisidia, indicating a certain degree of continuity. Occupation at the kastron continued until the 13th century CE, however it is likely that the destruction of the fortress on top of Alexander’s Hill in the early 13th century heralded the end of Sagalassos as an organized community. Afterwards, Sagalassos became part of the Anatolian Seljuk sultanate and occupation at the mountain slopes was abandoned in favour of the growing community in the valley bottom, which developed into the modern village of Ağlasun.