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

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