All roads lead to Rome… but where in Rome do they lead?

At the height of the Roman Empire (or at least at the height of the road-building part of the empire) twenty-nine highways spread out from the City of Rome into the lands beyond. You’ve no doubt heard the phrase “all roads lead to Rome” – the sentiment that you can reach the same destination by many different pathways.
(Side note: the first time that was written in English was in Chaucer’s technical manual on the astrolabe, which I wrote about in April of last year: “right as diverse pathes leden the folk the righte wey to Rome.”)
The Roman roads were lined with markers at each mile indicating the distance to Rome – the original milestones. This distance measurement was not to the outskirts of Rome, of course, but to its official centre. Before 20 BCE this was the Umbilicus Urbis Romae. Rome’s bellybutton was according to legend a sacrificial gate to the underworld, marked on the surface with a marble monument, and it was to the umbilicus that all the Roman roads ostensibly led. All that’s left today of the umbilicus is a rather underwhelming pile of masonry. Augustus changed the centre to a much more impressive monument known as the Golden Milestone (Milliarium Aureum) in 20 BCE, but that’s long gone now and we don’t know exactly where he put it.
This idea, that there should be a marker to indicate the official centre of a city, has been carried over into today. In many capital cities there is a plaque, or a statue, or an obelisk, that is the official measuring point for all distances to and from the city: the Kilometre Zero.
In Cuba, the Kilometre Zero is a 25 carat diamond (pictured above); or rather, it’s the replica of one after the original was stolen and then secretly returned in 1946. Hungary has a big “0” statue. In Japan it’s in the middle of the famous Nihonbashi Bridge. In France a plaque is embedded in the square outside the Notre-Dame Cathedral. The United States doesn’t really do kilometres (with some exceptions), but there is a Zero Milestone in Washington D.C. not far from the White House. And they all owe the idea to Rome’s bellybutton.