Caecilia Metella, as all Roman matrons of good family, did not have a name - but she did get one of the most magnificent mausoleums ever built to perpetuate her memory. Or, rather, the memory of her as pure dynastic locus of the merger between the clans of her father, consul Quintus Caecilius Metellus Creticus, and her husband, quaestor Marcus Licinius Crassus. Roman women did not have a praenomen, and were only identified by their father's nomen (representing the gens or clan) and cognomen (the bit that specified to which family, or sub-branch of a clan, one belonged). So you see, this lady did not have a real proper praenomen (let's say, Jane Caecilia Metella, or something), but only the two standard surnames. Men also had a right to a fourth name or agnomen, theoretically a nickname, but in fact a third surname that made the kinship structure even clearer. In any case, her mausoleum dominates a hill along the Appian Way since the first century BC, having been built approximately some time between 25 and 10 BC. The mausoleum is basically a huge tumulus, a drum made out of earth and clad in stone. Still today it looks both imposing and scarily simple, just a very large static mass. However, Piranesi's plate above shows how this building without an interior is far from being a one-liner.
The facade above cannot express the actual size of the building; the diameter is 30 m, the height 20 m. The scale of the stones used is very large, making the image look deceptively normal. In fact, the mausoleum was so big that throughout the middle ages it was used as a fortress, and it had a second life between 1300 and 1500 as centre of the headquarters of the Caetani family. It might not be obvious, but building something this large, even if it is (almost) only a sculpture implies some major engineering challenges.
The section is in fact rather inaccurate as the tomb is built on top of a layer of concrete almost 1 m thick laid on top of the existing hill which is made out of volcanic and tuff rock. Although obviously in Piranesi's time analysis techniques were not developed enough to know this, it is still rather surprising to see such a sketchy foundation section as throughout the Roman Antiquities Piranesi is almost more interested in the foundations than in monuments themselves. Still, the section shows the interior of the tomb, with the tapering, tall cella, which would have culminated with an oculus on the roof that was a simple grass-covered mound. This kind of mausoleum was quite popular and Hadrian's tomb - today Castel Sant'Angelo - follows the same model. Perhaps, the mound is a nod to Etruscan tradition?
Caecilia Metella might have never rested in the building - burial customs varied during the centuries of Rome's hegemony and at that point the deceased were most often cremated. Outside of the city walls, the first miles of the Appian Way were bordered by a series of tombs, memorials, cenotaphs, as it was impure to bury the dead in an urban area. In fact some, if not most, of these monuments did not actually mark a burial place but they simply ensured maximum visibility to the family of the deceased. The road was one single monumental space where citizens (and in some case rich freedmen) represented their status. Caecilia Metella's tomb would have stood out also in antiquity, not only for its scale, but for its higher topographic position. Although the tomb has almost no function, and almost no interior, it is still a rather awesome piece of architecture that contains many interesting details, both hidden, and visible.
As a footnote, if you are wondering what's the use of the agnomen or third Roman surname, let us say that this Caecilia Metella could have definitely used one - if only to distinguish her (daughter of Metellus Creticus) from Caecilia Metella (daughter of Metellus Celer). While our Metella was a real lady who only made the news in case of the proverbial 'hatch, match, and dispatch' (so much so that we know nothing at all about her), Metella Celer was a notorious socialite of the 1st century BC. Celer means fast, and indeed Metella Celer was not one to waste time as she happily ignored her own husband to help Dolabella cuckhold his wife. A wife who just happened to be Cicero's daughter... which as you can imagine did not help this Caecilia Metella get the best press. Then again, if the wife was as boring as the father, who can blame Dolabella?
Long story short: don't believe what they tell you about a Roman lady. As they didn't have a proper name and surname, you never know whether you're really talking about the right person.