221B Baker Street is a location featured on BBC's Sherlock. It débuts in the first episode of the first season.
221B Baker Street is based on the location of the same name from Sherlock Holmes novels.
221B Baker Street is the address of the Watson family, Sherlock Holmes, and Mrs. Hudson. Sherlock and John live in the apartment above. Mrs. Hudson also owns 221C below. Mrs. Hudson allows Sherlock to rent out the flat with a lower rent pay as a debt after he ensured the execution of her husband. ("A Study in Pink")
Sometime after the ordeal with Eurus, the flat is restored to its former glory, including the bullet holes and the yellow smiley face Sherlock put in the wall. After the flat is re-built, John and Rosamund move back into Baker Street.