Henry VIII's wine cellar at the Palace of Whitehall, built in 1514–1516 for Cardinal Wolsey, is in the basement of Main Building, and is used for entertainment. The entire vaulted brick structure of the cellar was encased in steel and concrete and relocated nine feet to the west and nearly 19 feet (5.8 m) deeper in 1949, when construction was resumed at the site after World War II. This was carried out without any significant damage to the structure.

Answer this question, if possible (if impossible, reply "unanswerable"): What is the main material used to build the cellar in the basement of Main Building?
brick