The Oria region. The Oria basin is the central region of Gipuzkoa, the most extensive, the one with the largest number of villages. Although it is the most important river in Gipuzkoa, its geographical size does not reach that of the Ibaizabal in Bizkaia. In Gipuzkoa there is no powerful semi-coastal mountain range blocking the course of the rivers and giving rise to a single large river and a series of independent watercourses as in Bizkaia. The Urumea, the Oria, the Urola and the Deba have a long independent course all the way to the sea. They are, with the Guipuzcoan-Navarrese Bidasoa, like the five fingers of one hand stretched out to the sea. The Oiartzun is an exception, it has the style of the small Biscayan rivers of the estuary region. The Oria is the middle finger of this river hand that comes out of the Aitzgorri, the longest. The fork that forms in Beasain with the two branches of the Oria coming from Zegama and Zumárraga-Villarreal formalises its course there. From here it flows onwards through the paper mill area towards Tolosa. The Lizarrusti-Ataun, Aralar-Amezketa, Azpirotz-Lizartza, Urto-Berastegui-Ibarra and Leitza-Areso-Andoain areas all reach its sparkling banks. The capital of this area is the historic Tolosa, the natural centre of its middle basin. The Oria flows past mountains full of white farmhouses and meadows full of factories. Its lazy course stretches as far as Orio, its dirty waters sweeping through the rich corner area of Aginaga. The Oria basin is the widest in Gipuzkoa, with the broadest horizon. The area of the Urumea brings water from the Navarrese wilderness of Goizueta and Artikutza. The lower basins of the Oria, Urumea, Oiartzun (Pasaia pass) and Bidasoa are only separated by slight obstacles. They can be considered as an expansion of the main Oria region. For the expansion of this population, in addition to the beaches from Orio to Hondarribia and Hendaye, it has at its disposal the whole of the immense Navarrese area that surrounds it from north-east to south-east with Aralar in its central part.