Echoriad

The Echoriath or Encircling Mountains were a mountain range in the north of Beleriand.

The Echoriath formed a natural circle of rock, enclosing the valley later called Tumladen, within which lay the Elven city of Gondolin. A hidden ravine provided the only access through the Echoriath — a way guarded by seven gates.

Etymology

Echoriath is Sindarin. It means "encercling fence", from echor "encircling" and iâth "fence".

Christopher Tolkien mentioned that his father's intent was to rename the Echoriath as Echoriad, but perhaps this knowledge eluded him while publishing The Silmarillion.