Saint Peter's Basilica half-built, the Colosseum in ruins and a blank space where the Trevi fountain now stands: computer whizzes rebuilt 16th-century Rome, with a twist, for the latest instalment of the video game phenomenon "Assassin's Creed".
Set for release next month, "Assassin's Creed: Brotherhood" continues the Renaissance tale of betrayed nobleman Ezio Auditore Da Firenze, a descendent of the Altair character who starred in the original title.
"Brotherhood" casts the player as Ezio, a trained killer whose mission is to combat the Knights Templar in the Eternal City.
Street by street, the hero weaves his way through a packed crowd: beggars asking for alms, city guards keeping a watchful eye on the throng, doctors in long-beaked masks offering remedies and potions.
To complete his assignment, Ezio scales the walls of buildings, and vaults from rooftop to rooftop, offering the player breathtaking views over the virtual cityscape.
Working with 16th-century maps and records, with the help of historians, developers at the French video game titan Ubisoft worked to recreate Rome as it looked at the time.
A stay in the city was par for the course to photograph bricks and rocks in order to recreate the feel of the original buildings, producer Vincent Pontbriand told AFP during a walk through the streets of the Rome to illustrate the design process.
But the Internet helped a lot too, according to game designer Patrick Plourde: "In a few minutes you can check on a detail that would have taken much longer before."
Details are as lifelike as possible, from the clothes of passers-by to the weapons used by guards or the walk-on parts -- which include the politician Cesare Borgia, the philosopher Niccolo Machiavelli and Leonardo da Vinci.
But the developers take liberties with history too -- as with the roof of Saint Peter's Basilica which was not yet under construction at the time the game is set.
"We tried to do without it, but no one recognised the building," said Mohammed Gambouz, creative director for the game at Ubisoft's Montreal studios.
"As soon as we added it, people looked and said, 'Ah! Now you can tell it's Rome'."
Likewise the Roman arches shown in the virtual city are all identical. "We mixed up several arches to create a single one -- that doesn't exist for real," said Gambouz.
The developers also played with building proportions to make the game's environment visually coherent.
In its virtual Rome, the Sant'Angelo castle towers over the city. Opposite, the Colosseum is outlined against the horizon and the player has to gain access to the amphitheatre to complete part of his mission.
But the Colosseum was scaled down to a quarter of its real size, while the Arch of Constantine was left proportionally larger -- "so it did not look ridiculous in comparison," explained Pontbriand.
At the time, the fourth-century arch had yet to be restored following damage from an earthquake -- but to the knowledgeable eye, the arch's shape has clearly been stretched, from elliptical to circular.
"We designed three different versions of the monument," said Gambouz. "We finally went with this one because of physical constraints linked to the Playstation 3 and Xbox 360."
The fifth instalment of the blockbuster franchise, "Assassin's Creed: Brotherhood" is being released on November 16 in North America for both videogame consoles, and two days later in Europe.
Explore further: Security CTO to detail Android Fake ID flaw at Black Hat