There a very useful feature in JOSM which I just discovered now: when looking at the history diffs of an object and you choose the coordinates tab, you get a map visualizing the geometry in a map.
From time to time people are moving the Rome node.
I found it interesting to see how the position changed by the time. This is the complete position history of the Rome node:
The node creation on 2007-10-15. Back then the local map was empty and a node anywhere near the centre was perfectly fine, but the editor decided after 10 minutes he could do better and already refined to a location close to where the central point commonly is associated with (the Campidoglio).
A further refinement on 2007-10-22. Now the position is perfect (for our means), it indicates the centre of the Campidoglio with the equestrian statue of Marcus Aurelius.
This is the Piazza del Campidoglio with the equestrian statue in the centre, you can also note the concentric pavement structure indicating the centre:
Now comes a longer period of people "touching" the node without actually changing it noticably. Take a look at the distance indicator:
Until someone comes along and decides in 2011 to relocate the centre close to the Spanish Steps (although this is a famous place, it is not generally considered the "centre point":
Just one minute later, the same user slightly adjusts the position, but keeps it at the Spanish Steps (Piazza di Spagna):
6 months later I relocate the node to the Capitoline Square (Piazza del Campidoglio):
3 years later another user starts readjusting the exact position (maybe in an attempt to optimize the rendering label positions and reduce label omissions):
Some months later, the node is moved further away from the center to the border of the square:
3 months after this, there's a new significant relocation, this time to Piazza Navona (while it is an important place, it is not the "centre"):
The same use relocates the node, 2 months later, to the Piazza delle Rotonda (square in front of the Pantheon):
That's where we're still right now, but I think I will relocate it to where I believe it belongs and where most of the other mappers also have seen for it the place to be. Well, actually there's another spot which might be brought into discussion as well: it is the place of a column just a stone's throw away on the Roman Forum, close to the temple of Saturn, errected the Emperor Augustus, which is the official start point of the "Vie Consolarie" (main arterial roads, historically until today).