Question: Given the following passage  "Public demand caused the government in October 1940 to build new deep shelters:189–190 within the Underground to hold 80,000 people but were not completed until the period of heaviest bombing had passed. By the end of 1940 significant improvements had been made in the Underground and in many other large shelters. Authorities provided stoves and bathrooms and canteen trains provided food. Tickets were issued for bunks in large shelters to reduce the amount of time spent queuing. Committees quickly formed within shelters as informal governments, and organisations such as the British Red Cross and the Salvation Army worked to improve conditions. Entertainment included concerts, films, plays and books from local libraries.",  answer the following question. Note that the answer is present within the text.  Question: Where in the Underground were shelters built?
Answer:
deep