It is often said that the 1993 WTC bombing was under the north tower and threatened to take the tower down. This is a myth.
The fact is that the bomb was in the parking garage under the Vista Hotel (WTC3) and did only superficial damage to the tower structure.
Popular Mechanics (July 1993) shows a diagram of the damage, which was outside the footprint of the North tower.
As you can see, the bomb damaged the refrigeration plant on the B5 level, which was outside the perimeter wall of the North tower.
Take a look at the strength of the tower during construction. How could this small bomb affect its overall integrity?