Read this and answer the question. If the question is unanswerable, say "unanswerable".

Plymouth has a post-war shopping area in the city centre with substantial pedestrianisation. At the west end of the zone inside a grade II listed building is the Pannier Market that was completed in 1959 – pannier meaning "basket" from French, so it translates as "basket market". In terms of retail floorspace, Plymouth is ranked in the top five in the South West, and 29th nationally. Plymouth was one of the first ten British cities to trial the new Business Improvement District initiative. The Tinside Pool is situated at the foot of the Hoe and became a grade II listed building in 1998 before being restored to its 1930s look for £3.4 million.

What notable location was named a grade II listed building in 1998?
Tinside Pool