Michael Terner sent me this great Map in the Wild from Madrid. It is sited at the centre of the Spanish national road network, when you are driving towards Madrid and you see a road marker measuring the distance to Madrid they are all measuring to this point.
In London the “central point” is the statue of King Charles 1st close to Charing Cross at the junction of The Strand and Whitehall. Where is the centre of your city? Send us a picture if you can.