"... Iran's nuclear facilities are so deep underground that it would be difficult for Israel to wipe them out...unless....."

Newsweek, here

"...............or even significantly damage them, with a quick airstrike. In order to deal a serious setback to Iran's nuclear program, at least four key sites inside Iran would have to be hit, said one Western official, who asked for anonymity when discussing sensitive information. The facilities, however, are located in tunnels fortified by barriers more than 60
feet thick. According to this official and other U.S. experts, Israel does not possess conventional weapons capable of knocking out the facilities. Breaking through the thick shell would require, at minimum, several bunker-buster bombs striking precisely the same spot. "These targets would be very hard to destroy," said former U.N. nuclear expert David Albright. Theoretically, Israel could do a lot more damage with a nuclear strike. But U.S. and other Western experts say there is no reason to believe the Israelis will abandon their policy against shooting first with nukes..."