Well, yesterday's quizz was easy-peasy, yes?
George Thornton was a mayor of Sydney, and mayors are very keen on getting their name on public amenities. This structure, on the T-intersection of Bathurst St with Elizabeth St, was erected in 1857 when Thornton was mayor. Being a sewer vent, it was quickly given the sobriquet 'Thornton's scent bottle'. It is modelled on Cleopatra's Needle in London.
You will be pleased to know that in 1965 the Benelong Sewerage System, of which this was the only ventilation shaft, converted to a storm water only system, still entering the harbour beneath the Opera House.