The Glauberg plateau was first settled in the Neolithic era (ca. 4,500 BC) by people of the Rössen culture. This was followed by a large settlement of the Michelsberg phase (4,000 BC). Michelsberg hilltop fortifications are known elsewhere, so it is possible that the hill was fortified for the first time at that stage. The hill was also settled by the late Bronze Age Urnfield culture (1,000–800 BC). During the Celtic late Hallstatt/early La Tène period, the Glauberg became a centre of supra-regional importance. At this time, it was the seat of an early Celtic prince. Extensive fortifications were erected.
During the Roman occupation of Germany, the Glauberg remained unoccupied, probably due to its proximity (5 km) to the fortified Limes Germanicus border. In the 4th and 5th centuries AD, it was reoccupied and became a regional centre once again, as the seat of a local king of the Alamanni. From the 7th to the 9th century, it was the site of a large Frankish fortification. Its importance grew throughout this time, and the fortifications were renewed and extended considerably.
In the 12th and 13th centuries, the Glauberg was incorporated into the Staufer system of castles, perhaps in an attempt to foster the growth of an urban centre. The fortifications were renovated again, and a tower-like castle was erected on the edge of the plateau; its arched romanesque doorway survives. The whole plateau was settled at this time, medieval foundations of walls, wells and basements survive especially at its north edge. The destruction of that castle, and with it the end of human occupation on the hill, probably occurred in 1256.
The earliest known fortifications might be pre-Celtic, but they reached a high point in terms of size and elaboration around the 6th or 5th century BC. They remained in use until the 2nd or 1st century BC. Their extent and dimensions mark the Glauberg as one of a network of fortified sites (or oppida) that covered most of south and west central Germany.
The northeast edge of the hill, where the slope is least severe, was disconnected from the adjacent ground by the erection of a massive ditch and bank, perhaps originally forming a promontory fort. The southern and northern edges were also fortified with walls. The walling techniques included drystone walling, the murus gallicus (a typical Celtic technique of wood and stone) and perhaps also mudbrick.
The small hilltop pond would not have sufficed to ensure water supply for the population of so large a settlement. For this reason, an annex was added to the north, with two walls running downslope, enclosing an additional triangular area of 300 x 300 m, including a spring. The point of that annex contained a huge water reservoir, measuring 150 by 60 m. At this time, the fortification was 650 m long, nearly 500 m wide, and enclosed an area of 8.5 ha.
At least two gates, a main one to the northeast and a smaller one to the south, gave access to the interior. They are fairly complex in shape, designed to make access for a possible attacker more difficult. An outer fortification was placed beyond the northeast edge of the oppidum. Walls or banks to the south probably played no defensive role.
Such settlements probably housed populations numbering in the thousands. For this reason, combined with their centralising economic role, Celtic oppida are sometime described as proto-urban. Nonetheless, little is known about settlement and other activity on the interior of the site. Evidence from the sites at Manching or Oberursel-Oberstedten suggests that there was probably a village or town-like settlement with houses, workshops and storage areas.
During an exploratory overflight in 1988, local antiquarians recognised the traces of a large tumulus in a field 300 m south of the oppidum. Between 1994 and 1997, the State Archaeological Service of Hesse excavated it. The mound (mound 1) originally had a diameter of nearly 50 m and a height of 6 m. It was surrounded by a circular ditch 10 m wide. At the time, it must have been a visually extremely striking monument. The tumulus contained three features. An empty pit was placed at the centre, perhaps to mislead potential looters. To the northwest, a wooden chamber of 2 x 1 m contained an inhumation, and to the southeast, a cremation burial had been placed in some kind of wooden container. Cremations are more commonly associated with the Halstatt phase, inhumation with the La Tène one.
The occupants of both graves were warriors, as indicated by their accompanying material: swords and weaponry. The chamber with the inhumation was extremely well preserved and had never been looted. For this reason, it was decided to remove the whole chamber en bloque and excavate it more slowly and carefully in the State Service laboratory at Wiesbaden. The finds from the main burial chamber include a fine gold torc and a bronze tubular jug.
A second tumulus (mound 2), 250 m to the south, was discovered later by geophysical survey. Erosion and ploughing had made it totally invisible. About half the size of mound 1, it also contained a warrior, accompanied by weapons, a decorated fibula and belt, and a gold ring.
The high quality of the tomb furnishings as well as other features associated with them indicate that the graves, and their occupants, were of extremely high status. They are therefore classed as "princely" burials, on a par with other well-known finds, including those at Vix (Burgundy, France), and Hochdorf (Baden-Württemberg, Germany).
The lack of a defensive function and the focus on the burial mounds have led to the suggestion that the enclosure and road system had a ritual or sacred significance. Such a complex is, so far, entirely unparalleled in Celtic Europe.
Much international attention was attracted especially by the discovery of an extremely rare find, a life-sized sandstone statue or stele, dating from the 5th century BC, which was found just outside the larger tumulus. The stele, fully preserved except for its feet, depicts an armed male warrior. It is made from a type of sandstone available within a few kilometres of Glauberg. Much detail is clearly visible: his trousers, composite armour tunic, wooden shield and a typical La Tène sword hanging from his right side. The moustachioed man wears a torc with three pendants, remarkably similar to the one from the chamber in mound 1, several rings on both arms and one on the right hand. On his head, he wears a hood-like headdress crowned by two protrusions, resembling the shape of a mistletoe leaf. Such headdresses are also known from a handful of contemporary sculptures. As mistletoe is believed to have held a magical or religious significance to the Celts, it could indicate that the warrior depicted also played the role of a priest. Fragments of three similar statues were also discovered in the area. It is suggested that all four statues once stood in the rectangular enclosure. Perhaps they were associated with an ancestor cult. Parallels to the Glauberg warrior statue exist in the form of stelai from other La Tène sites, such as the Holzgerlingen figure (Stuttgart State Museum), a pillar-stele from Pfalzfeld (St Goar), the Warrior of Hirschlanden and others.
The 16 postholes associated with the mound and enclosure have recently been interpreted as a simple astronomical calendar, to determine seasonal events or holidays.
Sites like Glauberg, sometimes referred to as Fürstensitze (seats of princes), indicate a parallel development of social hierarchies developing across late Hallstatt Europe. Elite sites, characterised by massive fortifications, the presence of imported materials and of elaborate burials developed along the important trade routes across the continent. Glauberg must now be considered a proto-urban centre of power, trade and cult, of similar importance to such sites as Bibracte, or Manching, but especially of other "princely" fortified settlements, such as Heuneburg, Hohenasperg and Mont Lassois.
Some of the finds from Glauberg, including the statue, are currently on display in the Hessian State Museum at Darmstadt. Due to the importance of the site, a new museum of Celtic archaeology is being planned for Glauberg itself, to house and explain the important objects near the location where they were found. Construction is to start in 2007, with completion projected for 2009.