impenetrable

A separate thread in the series follows the McConville children over the decades, as they fight an impenetrable code of silence to uncover the truth about their mother.

South Korea’s frontier with the North is an almost impenetrable barrier, the heavily mined and fortified Demilitarized Zone.

Suriname has some of the most impenetrable jungle in the world, covering 93% of the country.

This so-called iron wall had long been viewed by the IDF and people across Israel as impenetrable, and yet bases along it began reporting breaches.

The woodland environment - dense thicket and brambles - made it "impenetrable" to zoo volunteers.