From the thousands of people who pass it every day, few give the non-descript iron bollard a second thought, but the piece of street furniture is actually rather important.
Get the latest nostalgia features and photo stories from Edinburgh straight to your inbox Traffic Bollard
Get the latest nostalgia features and photo stories from Edinburgh straight to your inbox
To the thousands of locals and tourists who walk past it every day, it's just another bollard - and yet it's probably more important than any other in Edinburgh.
Facing Register House at the east end of Princes Street stands a mundane-looking cast iron bollard that most people breeze by without giving a second thought, but if it wasn't there we'd all be technically lost.
Its importance stems from the fact it's sited outside what was once Edinburgh's General Post Office (G.P.O.) building, the Waverley Gate offices at Waterloo Place, with the marker used to precisely measure all distances to and from Edinburgh.
READ MORE: Sneak peek inside Edinburgh's old Odeon cinema as images show work underway
What's more, all post codes and street numbers in Edinburgh emanate from the bollard, making it more important than any other of its kind.
In other words, forget Edinburgh Castle, the High Kirk, or any other major architectural landmark, this non-descript metal post marks the city's true centre.
The distance marker was this week the subject of a TikTok video by prolific Edinburgh content creator Mr Broonford.
In the clip, which has been favourited more than 14,000 times, Mr Broonford told followers: "Behind me here is probably the most ignored thing in Edinburgh. This post here might look like it's just another barrier, but you'll notice there are no other barriers round about it that are the same.
"And it's because it's actually very important. The building beside it here used to be the G.P.O., the General Post Office, and this post right here does three very important jobs.
"From this point every post code in Edinburgh goes out from here. Also, any street number starts with its lowest number closest to this post. And last, if you're coming to Edinburgh from anywhere and you see a sign, for example saying '10 miles to Edinburgh', it is 10 miles to that point".
Responding to the video, Mr Broonford's TikTok followers were thankful to have learned something new about the capital, with many admitting their minds were blown by the info.
Sign up to our Edinburgh Live nostalgia newsletters for more local history and heritage content straight to your inbox
Grahamw444 said: "I've lived in Edinburgh all my life and never knew that cheers for sharing."
Anouska Curzon posted: "Literally the most interesting thing I’ve heard all week. Thanks for the insight."
Marynorn wrote: "I am ridiculously excited by this! My Grandfather worked in the GPO and until now, I’d forgotten him telling me this 40+ years ago."
Ashley Greenhorn707 added: "I didn’t know that!! I used to work In that’s building and wondered why it was different."
Not all UK towns and cities use general post office markers to pinpoint their centre. Some places consider their town hall to be the point from which distances are measured, while others give landmarks such as churches and market places the honour.
Commenting on the peculiar origins of the UK's distance markers in 2016, historian David Long told the BBC: "My suspicion is some bureaucrat decided quite arbitrarily to say it was this spot and it has just become enshrined. Something difficult for us to appreciate is the often ad-hoc nature of these things.
Modern Bollard Mr Long added: "I suppose it is only really useful from a road sign point of view. For those people living somewhere, where exactly the centre is does not really matter."