These are two from the total of twelve plates that make up Ligorio's imaginative reconstruction of ancient Rome. This work is not a map or a footprint of the city, but rather a representation, an image, a picture of ancient Rome. The bird's-eye view of the city was the result of twenty years of intensive research and study of classical literary sources, extant ruins and fragments, antique inscriptions on bronze, lead, stone, and terra cotta, and depictions of temples and monuments on ancient reliefs and coins. This project was Ligori's attempt to visually restore the ruined city in order "to refresh and preserve the memory of ancient things, and...to satisfy those who take delight in them." Note that in the Circus Maximus, below the Colosseum in the lower plate, Ligorio has placed the two obelisks brought from Egypt on the central barrier of the racetrack--a detail that at the time was known only from ancient literary sources.
Not only does Ligorio base his reconstruction on antique evidence, but he also represents the buildings and monuments in the same manner as an ancient artist would have depicted them rather than according to the linear perspective invented in the Renaissance. To enhance the sense of a great city, Ligorio has filled the spaces between the major monuments with representations of ordinary houses and apartment buildings, whose designs seem to be based on an ancient relief.
Only one impression of the original edition published by Michele Tramezzino in 1561 survives today, it is in the collection of the British Museum. This impression comes from an eighteenth-century edition issued by Carlo Losi in 1773, the same edition that is held by the Vatican Library.