In response to the London Zoo comments:
I actually really like London Zoo, it has a fascinating and extensive history; and when I visited, I thoroughly enjoyed viewing the architectural highlights (including the many heritage listed exhibits) like the Snowdon Aviary, the Casson Pavillion, and Mappin Terraces and the Lubetkin Penguin Pool.
I won't deny that few of the heritage listed exhibits are still suitable today for their original purpose (i.e. housing elephants); but I enjoy nothing more than seeing architectural wonders re purposed for modern day use where possible.
I'm apparently in the minority here; but for me, London Zoo was underrated in my opinion!