To the north of Dimbar, the Echoriath or Encircling Mountains rose in sheer cliffs. From one of these cliffs ran the Dry River, and at its end was an opening in the cliff face. This cavern mouth appeared to be natural, but it led into the Hidden Way, a dark tunnel that ran into the Mountains and ended at the Dark Gate. From that guarded Gate the tunnel emerged into the Orfalch Echor, the narrow ravine that led through many further gates to the plain of Tumladen and the Hidden City of Gondolin. After the disaster of the Nirnaeth, King Turgon commanded that even the Hidden Way should no longer allow entrance to the city, and it was sealed with stones.