Conversation so far:
where does harry potter get his school supplies
Hagrid explains that Harry Potter will buy what he needs for school in Diagon Alley.
is diagon alley accessible from london
Diagon Alley is accessible from Muggle London through the Leaky Cauldron, which is on Charing Cross Road, set between a bookshop and a record shop

Question: what is the cauldron
Self-contained rewrite: what is the leaky cauldron