The mausoleum was built at the third mile of the Appian Way in the years 30-20 BCE, on a dominant position overlooking the road, just at the point of arrestation of a leucite lava flow ejected 260,000 years ago from the Alban Hills volcanic complex.
It is a monumental tomb erected for a Roman noblewoman whose degrees of kinship are known, albeit only partially, thanks to the inscription, still preserved. Her father was Quintus Caecilius Metellus, consul in 69 BCE, who, between 68 and 65 BCE, conquered the island of Crete, whence he derived the agnomen Creticus; her husband was, in all probability, Marcus Licinius Crassus, who distinguished himself among Caesar’s retinue on the campaign in Gaul and was the son of the celebrated Crassus, member of the First Triumvirate along with Caesar and Pompey.
The monument consists of a quadrangular basement of concrete, made of flintstone flakes, originally sheathed with blocks of travertine, only some heads of which, embedded in the core, are today preserved, because of the repeated spoliations of the Renaissance; upon this base rises an imposing cylinder, still clad with the original travertine slabs, on whose summit is a marble frieze decorated with bucrania and garlands of flowers and fruits, interrupted by a high-relief with a trophy of arms and the figure of a barbarian prisoner with his hands bound behind his back. Probably the cylinder was originally surmounted by an earthen barrow covered with vegetation.
The interior of the tomb consists of a funerary chamber of slightly conical shape about 6.50 metres in diameter, occupying the whole height of the cylinder, open at its top with an oculus and sheathed with a brick curtain of excellent workmanship.
Today the summit of the mausoleum is crowned by an extra storey in brickwork of small peperino blocks which retains the Ghibelline battlements relevant to the modifications carried out by the Caetani family in order to transform the sepulchre into the keep of their castle, subsequently enclosed in the larger Castrum Caetani (Caetani Castle).