In answer to the questions on what this is - it is an old shot tower inside a shopping centre. The roof is a cone shape. The shottower is a listed building in Melbourne and so when they built the shopping centre they had to preserve the building - so they have incorporated it into the design.
A shot tower is where they would make the little buckshot in shotgun cartridges, etc. in times gone by. I believe it was done by pouring molten lead from the top of the tower, letting it form into drops and solidify before landing in a water container (I believe) at the bottom of the tower.