The tomb is located to the west of the citadel of Mycenae, approximately 70m from the Lion Gate, in an area used for burial since the Middle Helladic period (c. 2000–1600 BCE).
[1][2] Its structure follows the typical tripartite division of Mycenaean tholos tombs into a narrow rectangular passageway (dromos), joined by a deep doorway (stomion) to a burial chamber (thalamos) surmounted by a corbelled dome.
[4] A 'relieving triangle' was built above the tomb's lintel, helping to direct the stress from the weight of the masonry towards the supported ends of the lintel-stone and therefore to reduce the torque applied to the stone.
[5] Other innovations include the lining of the dromos with rubble and the use of poros ashlar masonry for the façade, both of which foreshadow architectural conventions common in later tombs.
[9] During the excavation, Wace incorrectly concluded that the Tomb of Aegisthus had no relieving triangle, a judgement which remained the scholarly consensus until 1997,[10][a] when the area above the lintel was cleared during conservation work.
The work revealed that the interior of the triangle, photographed by Wace in 1922, had been filled with a blocking wall some time after its initial construction, though the intrusion of much-later ceramic material into the space, partly as the result of an earthquake, made it impossible to ascertain the precise date.
Evans's work on Crete raised questions as to the origins and development of the 'Mycenaean' civilisation, labelled as such after Heinrich Schliemann's 1876 excavations of the Shaft Graves at Mycenae.
[34] In Evans's mind, his discoveries at Knossos proved that Crete was the centre of the dominant power of the Bronze-Age Aegean, in line with the Classical myths of a Cretan 'thalassocracy' under King Minos.
[d][1] With some assistance from Evans, the British School at Athens persuaded both the Greek government and Christos Tsountas, who held the permit, to allow them to excavate with Alan Wace as field director.
[1] Evans had been particularly keen for the excavation of the Tomb of Aegisthus, and donated £100 (equivalent to £5,074 in 2023) towards that project,[1] believing that the exercise would provide confirmatory evidence that 'Minoans' had risen to dominance at Mycenae between the Shaft Grave period (c.1600–1450 BCE) and the construction of the tholoi.
Among the finds were small fragments of an ivory carving, which Wace reconstructed as being similar in design to the relief of the Lion Gate, approximately 20 cm wide.
[41] Several Palace-style piriform (pear-shaped) jars, made on Crete during the LM II period (c. 1440–1400 BCE),[2] were found in fragments trodden into the floor of both the dromos and the thalamos, providing strong evidence that they were part of the earliest burial assemblages in the tomb, and therefore helping both to date the monument and to provide evidence of connections between Mycenae and Minoan Crete in this period.
[42] Wace and Lamb had planned to excavate the tomb in its entirety between 1922 and 1923, but were unable to return in 1923 due to safety concerns about the partially-collapsed dome roof.
[44] By May 1923, Wace and Lamb had constructed the outline of a three-phase chronological model for the tholoi at Mycenae,[3] in which they argued for a progressive increase in the scale and monumentality of the tombs.
[51] Further conservation work was carried out by the Greek Archaeological Service in 1997–1998 to reinforce the internal structure of the tomb,[50] which also revealed the existence of the small relieving triangle above the lintel.