in 1969 I was living in St Albans, a western suburb of Melbourne and not all that far from Tullamarine Airport. At the time Tulla was still being constructed and I as a newly turned 15 year old rode my bike everywhere, including across the steep valley sculpted by the Maribyrnong River between St Albans and Keilor. From Keilor it's a short ride to Tulla.
So one afternoon in late 1969 I found myself riding along a very wide ribbon of concrete. This was one of the runways for the new airport (and doesn't that tell you of the innocence of the time - this was pretty much before the age of hijacking - can you imagine being able to get within a kilometre of an airport runway these days - even for an airport still under construction?).
By the luck of timing I had arrived just as the work gang were finishing up; and there in front of me was a freshly laid batch of concrete. Admit it, you'd have done the exact same thing I did. I made a palm print in the fresh concrete.
I'd be enormously surprised if it was still there; and I never had the opportunity to go back and check.