Hi V .. This is the dome of the Royal Exhibition Building, 9 Nicholson Street, Carlton Gardens in Melbourne. Construction of the building was completed in 1880 and it hosted the Melbourne International Exhibition from 1880-1881. It was the site of the sitting of the first Parliament of Australia upon Federation in 1901.
In the 1880's visitors were able to access the exterior of the dome from a promenade deck which I am guessing is the area pictured around in the dome in the aerial view above. One visitor described the experience:
"At one's feet lies the city, with its well-planned and equally well-executed streets, its commendable buildings, its domes, its churches and its towers. Then the suburbs, green almost as the country beyond end the water of Port Phillip ... The sight was grand enough to be subduing ... and as we filed down the apparently endless stairs it was to the tune of silence."
Recent reports indicate that there are plans afoot to re-open the "Roam the Dome" experience enjoyed at the People's Palace over a century ago .. .J.