No worries , Wishfull.
I only know a little bit because i have only been living and working in the ballarat area for 15 years.
Have a read of this
https://savecivichall.org/history/ . Anne is our top historian and explains this very well.
The area was a stockmarket area ( Hence , Market street is only 30 yards away ) and the building i worked in across the road was previously a produce, petrol and general goods merchant by the name of A.W. Hancock, back in the day. At the back of that was a stockmarket , Irwin`s had a row of buildings on Lydiard street north directly behind Hancocks with hotels and hardware stores going north up to the railway tracks ,with Ludbrook House being one of those buildings and i believe that was where returning ww1 soldiers stayed on their way home and on the other side of the road next to the railway station was Reid`s coffee palace , i think they called it and now that is Reid`s guest house , a temporary accommodation place. Along that row of buildings were various pubs with deep cellars and other businesses. Gollars is one and still stands there,but not in use. I have been in the very back of one of the businesses next to Gollars and have seen one entrance to the underground tunnels that run behind all those buildings. Apparently a tunnel runs all the way along from Reid`s guest house and under all those businesses on Lydiard street and right down Mair street towards Bakery Hill where the Eureka Stockade was staged. 3 blocks south along Lydiard street past the mining exchange and old post office ,you get to the old jail ,which is now one campus of the Fed Uni. This was where the old jail was and there is a tunnel that goes from the jail to the courthouse down the hill to escort prisoners without fear of escape. Only a hundred yards north of there ,as the crow flies is the old Camp street Halls of Justice Police building ,now another Fed Uni campus and i`ll bet there is a tunnel from there to the courts ,too. I don`t honestly know. There is also a tunnel straight down the guts of the main street ( Sturt street ) filled with old shops and the council was going to let the public in to view them in tours, but turned around and decided against it. Bugger. Remember there would not be much air in there and setting it up to let tourists in might well damage a part of history.
Now , All these tunnels may join up at some point or various points and i don`t know how far up the hill they go or if they go west from Lydiard street towards the Civic a Hall site , so where the Civic Hall is , it is reasonably flat ground and was Crown land before The Alfred Hall . Being in an area of a great many hotels , a stockmarket and businesses and only 70 yards from Ludbrook House where the soldiers were , i wonder if it was an old dumping site . I might try to find out more during the week.
I have some of this info in books and will try to dig it up to post it here. I couldn`t find it this morning, but will endeavour to do so.
Sorry if i got sidetracked . Please correct me if my info is not quite right and other would have more knowledge than i do on Ballarat.
FOZ