Why are there several floors underground of Buckingham Palace Hotel in Shanghai?

Used as a parking lot. Shanghai Minhang Buckingham Hotel covers a total area of 8,600 square meters, with a total construction area of 99,707.29 square meters. The main body is concrete structure, including five-star hotel 13 floors and overground 17 floors. It has a four-story platform and a two-story underground garage. Upon completion, it will have more than 600 rooms, a pillarless banquet hall of 3,000 square meters, a 24-hour restaurant and nearly 654,300 restaurants.