With a total length of 13.3m, it is a dolmen with a vast chamber and corridor. The chamber is polygonal with seven pillars (6 still in situ) and is 4x6m in diameter. The foremost pillar is 4.4m high, 3m wide and 1m thick, weighing around 37 tons. Some of the pillars were removed or fractured, and the chamber overturned. The presence of three 15th-century coins signals one of the disruptive moments of the monument. The corridor is 8.6m long, and some remains of the tumulus (dolmen) that likely surrounded the chamber and corridor are still visible. The surface had fragments of shale, and, in the mid-20th century, the owner mentioned the existence to the south of the corridor of pits lined with slabs of shale containing human bones and ceramics. Thus, tholoi could be associated with the dolmen, as with the neighbouring Anta 2 do Olival da Pega 2, or the Comenda 2, Farisoa 1 or Cebolinhos 3 dolmens. A geophysics test a few years ago also suggests this.

Built at the height of megalithism (end of the 4th millennium BC), the large Alentejo dolmens, of which Anta Grande do Olival da Pega is a benchmark, served for collective burials for a prolonged period that extended into the 3rd millennium BC, accumulating remains of a large number of individuals and also votive materials. In this dolmen, despite the recorded disruptions, numerous human bones, burned and unburned, and immense archaeological materials were recovered: axes and adzes in polished stone, geometric shapes, blades, arrowheads, necklace beads, bone pins, slate slabs and crosiers with geometric decoration, zoomorphic figurines (rabbits), an anthropomorphic idol (Almerian type) in schist, ceramic containers (some with symbolic decoration with solar eyepieces), spoons and two cranial discs (possibly the result of trepanations carried out on human skulls).

Archaeological excavation in the mid-20th century by German archaeologists Vera and Georg Leisner.

LEISNER, G.; Leisner, V. (1985) – Antas do Concelho de Reguengos de Monsaraz [1951]. Lisbon. START; Gonçalves, V. S. (1999) – Reguengos de Monsaraz. Megalithic Territories. Lisbon. CMRM.