Task: Question Generation
Input (English): Melbourne's CBD, compared with other Australian cities, has comparatively unrestricted height limits and as a result of waves of post-war development contains five of the six tallest buildings in Australia, the tallest of which is the Eureka Tower, situated in Southbank. It has an observation deck near the top from where you can see above all of Melbourne's structures. The Rialto tower, the city's second tallest, remains the tallest building in the old CBD; its observation deck for visitors has recently closed.
Output (English): What building is the tallest building in the old CBD?