The historical site of Boğazköy (Hattusas) is located at 82 km to the southwest of Çorum and it is 208 km from Ankara. Boğazköy (Hattusas) site which was located at the core region of the Hittite state is at the southern end of the Budaközü River valley, at an elevation of 300 metres from the plain surrounded by numerous rock masses and the separations of mountain sides and deep cliffs to the north and west. The city is open towards the north and surrounded by city walls on all sides except the north.

The Hattusas historical site was first visited by Charles Dexter in 1834 and introduced to the world. Later Sayce made the first connection between with these ruins and the Hittite state as until that time the centre of the Hittites was considered to be in Syria. In 1882, Carl Human came to Boğazköy with Otto Puchstein and they, for the first time made a comprehensive planning study. They also made castings of Yazılıkaya which is currently at the Pergamon museum. During the years 1893-1894 E. Chantre carried out the first explorative excavation and in 1905 Makridi and H.Winckler visited Boğazköy and carried out the excavations which continued until 1917. The systematic excavations which were started in 1932 by Kurt Bittel on behalf of the German Archaeological Institute were stopped for a while during the World War II and the work was later resumed and continued under the same excavation leader until 1978. The excavations which are carried out under the leadership of Dr. Peter Neve from 1978 to 1993 is still progressing on behalf of the same institution by Dr. Jurgen Seer.

Settlements existed at the Boğazköy (Hattusas) site since 3rd millennium B.C.. The small and fortified settlements of that period were at Büyükkale and its environs. In the 19th and 18th centuries B.C. settlements from the age of Assyrian Trade Colonies are seen at the Lower City and the name of the city was first discovered from written documents of that era.

The first period of development at Hattusas terminated with a major fire and the culprit behind this fire must be the Kushara King Anitta. According to documents, right after this destruction, around 1700 B.C.. Hattusas was settled once more and became the capital of the Hittite state in 1600's and its builder was Hattusilis I. who had a Kushara origin just like Anitta.

After Hattusas became the capital, a monumental building development can be seen at the farthest point of the spreading settlement and the city took its 13 century B.C. form with 2 km wide palace and temple districts. In the second development period of Hattusas three important Hittite kings played a significant role during the last years of the Empire. They were Hattusilis III, his son Tudhaliyas IV, and his son Suppiuliumas II. When the Hittite state was destroyed due to economic hardships and internal strife during the last years of the Suppiuliumas II reign (1190 B.C.) Boğazköy was abandoned for a period of 4 centuries and the first settlement seen after this gap is Phrygian (middle of the 8th century B.C.) During the Hellenistic and Roman times (the 3rd century B.C. - the 3rd century A.D.) Hattusas is a fiefdom centre surrounded by a small wall and it appears as a village during the Byzantine period.

The part of Hattusas known as the Upper City is a sloped land of more than 1 square kilometre. This area has witnessed the development of the city during the late Empire Period in the 13th century B.C.. A major part of the Upper City solely consisted of temples and sacred places. Upper City is surrounded at south by a city wall which draws a large arch and this wall has 5 gates. At the furthest southern point of the wall and at the highest point of the city, the gate with the Sphinxes is located with its bastion rising above anything else. Of the other four gates the two facing one another at the southern and western tips of the city walls are the royal gate and the gate with the lion.

The building development seen in the Upper City has been in three stages. The first stage coincides with the construction of the city walls. The second is the stage of rebuilding and giving the temple city its final form following the first destruction of the walls. During the last stage a new construction activity had started besides the repairs and renovations carried out at the existing buildings for purposes other than the religious ones. In the Upper City, the area known as the district of the temples reaches from the gate with the Sphinxes to Nişantepe and Sarıkale. In this part many temples were revealed originating from different stages. The general characteristics of the temple plans were defined by the cult room groups which are entered from a central court yard and consist of a narrow fore-space and a deep main space. The material obtained from the temples is divided into five groups.
1- Utilized ceramics,
2- Utilized tools,
3- Weapons,
4- Cult objects,
5- Written documents.
In the Upper City Post - Hittite buildings at Nişantepe and Güneykale which are right at the front of Büyükkale are significant and this is the Phrygian settlement which is dated to the 6-7th centuries B.C.. For the Hittite period this area is studied in three sections defined according to the topography. The pass to the south of Büyükkale (Viaduct), the plateau which was previously settled which is to the north of Nişantepe on both sides of the roads leading to Upper City, and the area at the site of Güneykale.

The road network which connected to Nişantepe and the Upper City through the viaduct reaches a complex with a stone laid inner court with buildings on the north, south and east sides and a gate on the fourth.

An important building besides the northern and southern structures is the western building and the palace Archives. It is assumed that the building which was destroyed in a big fire had two basement floors on the slope. In these two basements nearly 3300 annals and 30 tablets with hieroglyph inscriptions were found. 2/3 of the annals carry the Great King seals and in chronological order represent Kings from Suppiuliuma I to the last king of Hattusas , his great son Suppiuliuma II. Queen seals besides the king seals were also discovered.

The construction at Güneykale was realized by Suppiuliuma II. There is a large artificial lake and three buildings on three separate points around it. Of the two buildings which are still standing and named Room 1 and 2; Room 2 is to the west of the northern corner of the lake. This room which has a single space has a parabolic dome which diminishes as it becomes narrower towards the inside. There were few remains found in situ in Room1. All three walls of room 2 are decorated with reliefs. The main picture on the opposite wall has a figure with a long garment which faces towards the left. There is a sundial with wings on the round head dress and the figure holds a lotus in the left hand and an anch motif in the right. On the west wall facing it there is a hieroglyphic inscription.

The excavations carried out at Büyükkale which is built on a hill of natural rock area to the south of the city proper has revealed the palace buildings of the Hittite Kings in the 13 - 14th century BC and the characteristics of the wall systems which were for their defence. The walls of the castle whose entrance gate is at southwest are built on beds carved into rock at north and south and on a piled earth level in the south with the chest wall technique. The palace building cannot be seen as a whole from Büyükkale. Buildings of varying types and sizes which were revealed with excavations, large interior spaces connected together with courts and columned galleries form the whole within the castle. The castle has rooms for archives and storage, a large reception hall, buildings related to the water cult and sacred spaces. The Remains of the Phrygian buildings were found at the castle following the Hittites.
One of the most important architectural sites at Boğazköy is the Great Temple (Temple no.1). The Great Temple which formed the centre of the northern city in Hattusas was built as the home of the Storm God of Hatti and the Sun Goddess of the Arinna City. The temple has two additions and there are stone paved roads and squares around it and storage rooms behind in all four directions open up to them are located behind. The Great Temple is separated from the districts of the Lower City with a wall. The Great Temple which is built on a stone terrace obviously served as an economic centre as well as a religious centre as the large jugs which are revealed in situ at the shops indicate. Again the tablets found at the eastern shops of the temple shows the existence of the archives.

The Great Temple is surrounded by buildings of secondary importance. Most important one among them is the Slope House. It deserves attention with its large size, its plan and the fact that it is a multi-storey building.

Excavations at the Hattusas historical site have been carried out at Büyükkaya since 1993. The discovered ceramics show that a small settlement which was first built during the Chalcolithic Age was still a settlement during the period known as the Dark Age. However the investigations have shown that there were large silos with stone paved floors during the Empire period. At Büyükkaya, which also witnessed the Phrygian period, settlements from the early Phrygian period are defined.