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 means something like 'outer circle fence' and can be analyzed as et-cor-iath. Cf. Rammas Echor.

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.