The maximum elevation at the source is 1,260 m, while at its lowest height the tidal influence extends inland up to Usurbil (estuary).

On this final stretch, many marsh and wetland strips dotted the banks of the Oria, although some of them have been drained for agricultural and building purposes.

The major road A-1 (European route E-5 E-80) runs along the Oria most of the time, as well as the Spanish Northern Railway, right from its rise on the slopes of Aizkorri.

There exists an unstable trout population downstream of Andoain, while other fish prevail and remain steady, i.e. Cyprinidae such as barbel (Barbus graellsi), ezkailu (Phoxinus phoxinus) and ray-finned fish (Chondrostoma toxostoma arrigonis).

A stretch of the estuary by the village Aginaga is known for its baby eels, bred and harvested for human consumption before they grow up, providing for a much appreciated and dearly paid delicacy, while they were totally neglected just some decades ago.