Although fortifications were built here by the Maccabees in the second century b.c. , King Herod the Great improved on these hugely, transforming them into a magnificent fortified palace, stocked with years' store of food and fitted with enormous cisterns (supplied by flash floods via an aqueduct) to ensure a plentiful water supply.
King Herod the Great built an aqueduct that filled cisterns.
Though it was built in the 18th century, the Royal Palace is actually in the old area of Madrid.