I visited some of the caves in the desert which were built thousands of years ago by non-Jewish tribes. In the middle of scorching summer the environment underground was cool and comfortable. Israel must build above and below the ground to protect its citizens. The units below ground must able to support life in case of ballistic, chemical, nuclear attacks. The costs would be astronomical, but life in ME calls for maximum protection.
Iran deal opposition grows among U.S. Republicans, Reuters poll shows (Reuters)
from the article: Why are Israel's politicians still prevaricating about rocket defense?