'The Great River' flowing from north to south and dividing West from East Beleriand. Passim; see especially 52, 141-2, 145. Falls of Sirion 203, 285. Fens of Sirion 203. Gates of Sirion 146. Havens of Sirion 294, 304-5, 313. Mouths of Sirion 60, 142, 190, 192, 239, 293, 302, 304. Pass of Sirion 135, 141, 182, 193, 215, 234, 237, 260, 265. Vale of Sirion 56, 124, 135, 140, 149, 248, 265, 301