Herod the Great built his fortress and palace 24-15 BCE atop a hill almost 2500 feet above sea level. This aerial photo (courtesy of Wikipedia) depicts how difficult it was for his enemies (and us) to ascend to the top. Cisterns, secret tunnels, and hidden apertures for sneak attacks abound.
These cisterns stored rainwater.
Do these wooden supports look adequate?
Secret tunnels were used by Jewish rebels during the great revolt against Rome in 66 CE and Bar Kochba revolt in 132 CE.