Eastern Mountains. From the Peñas de Aya (832 m.) that separate the basins of the Bidasoa and Oyarzun rivers, the series of heights continues through Bianditz (840 m.), Urdaburu (595 m.), Mandoegui (1,046 m.), Urepel (1,059 m.), Ulizar (866 m.) and Irumugarrieta (1,427 m.).
