Herodian architecture is a style of classical architecture characteristic of the numerous building projects undertaken during the reign (37–4 BC) of Herod the Great, the Roman client king of Judea. Herod undertook many colossal building projects, most famously his reconstruction of the Temple in Jerusalem (c. 19 BC). Many of his structures were built upon comparable, previous Hasmonean buildings and most of his have, in their turn, vanished as well.
Herod introduced numerous architectural innovations and construction techniques in his buildings, such as the domes inside the Double Gate to the Temple Mount. He adapted the mikveh — a Jewish ritual bath — for use as the frigidarium in the Roman-style bathhouses in his many palaces. Herod also developed an innovative combination of palace and fortress; examples include the Antonia Fortress in Jerusalem, the Herodium in the Judean Desert about 2 miles south of Bethlehem, and Masada. Characteristically, they have (or had) one tower higher and stronger than the others. Herod’s fortification innovations strongly influenced the military architecture of subsequent generations.
In line with contemporary Jewish customs, Herod generally avoided the representation of human and animal figures, even in the closed and private parts of his palaces.
In the eighteenth year of his reign (20–19 BC), Herod rebuilt the Second Temple in Jerusalem on "a more magnificent scale". The new Temple was finished in a year and a half, although work on out-buildings and courts continued another eighty years. To comply with religious law, Herod employed a thousand priests as masons and carpenters for the rebuilding. The finished temple, which was destroyed by the Romans in 70 AD, is often referred to as Herod's Temple. The Wailing Wall (Western Wall) in Jerusalem was for many years the only section visible of the four retaining walls whose construction was begun by Herod to create a flat platform (the Temple Mount) upon which his Temple was constructed. Recent findings suggest that the Temple Mount walls and Robson's Arch may not have been completed until at least 20 years after his death during the reign of Herod Agrippa II.