Passage: Due to the space restrictions imposed by the narrowness of the "tail", and the advantages of living within the defensive wall, the Old Town became home to some of the world's earliest "high rise" residential buildings. Multi-storey dwellings became the norm from the 16th century onwards. Many of these buildings were destroyed in the Great Fire of Edinburgh in 1824; the rebuilding of these on the original foundations led to changes in the ground level and the creation of numerous passages and vaults under the Old Town. The construction of new streets including North Bridge and South Bridge in the 18th century also created underground spaces, such as the Edinburgh Vaults below the latter.

Question: When did "high rise" dwellings become the norm?
16th century