In the most recent thread about the worst station in Melbourne, some made the suggestion that the former Spencer Street Subways should be reopened. For some reason, I was under the impression they had been filled up, but it turns out they are still there. This page provides some insight as to what became of them. Unfortunately, I don't think they will be reopened anytime soon as they appear to have been partially filled with utility services. What I found funny was that a $750,000 study was commissioned to determine whether the subway could be reopened to the public. I wonder if they actually spent that amount and why a graduate engineer with guided access through the tunnels and a month to research and write up a report couldn't have achieved the same thing for a fraction of the cost:

https://wongm.com/2021/07/uncovering-spencer-street-station-subway-remains/

Also came across this page sometime ago about the Degraves Street Subway at Flinders Street, after being curious as to why it looks like there's a filled up entrance near the northern end stairs:

https://www.museumoflost.com/the-degraves-street-subway/