Who built Tower of London?

Tower of London is a historic building in London, UK. It was built in 1070s by the Duke of Normandy, William the Conqueror after his victory at the Battle of Hastings in 1066. It was built as a castle but was mainly used for imprisoning and executing prisoners. In the 1600s, it was decreed that the tower must have 6 resident raven birds otherwise the kingdom itself would fall. Recently, the resident raven, Merlina went missing, sparking discussions about this old prophesy.