London ZOO - one of the oldest in the world

I've read that too somewhere... but now, of course the London Zoo has become one of the most progressive in the world. For example I was told there's a penguin pool designed somewhere in the '30s and is one of London's foremost modernist structures. still I believe the rhinos, elephants, penguins and all the species of birds make a visit to the zoo worthwhile by itself. for £14 per adult I'd go, if I were in London...