There was a menagerie in the Tower from the thirteenth century to the nineteenth. In 1235, Emperor Frederick II sent Henry III three lions (or leopards, it's not clear), as a wedding present, which were kept there. Towards the end of its existence, it was open to the public.
Most nobles were executed on Tower Hill, which was outside the Tower and open to the public. Seven people (William Hastings, Anne Boleyn, Katherine Howard, Jane Grey, Lady Rochford, the countess of Salisbury, and the earl of Essex) were executed on Tower Green, which was 'by invitation only'.