Slowly meandering toward the Sea of Biscay, the Oca River Estuary forms a vast wetland, the Iberian Peninsula's most important. It is protected by both the RAMSAR agreement and as a UNESCO Biosphere Reserve, the Urdaibai Reserva de la Biosfera is home to scores of seabirds and other wildlife.
Perhaps more importantly to some visitors, it is lined with wide golden beach and quiet coves of soft sand, undulating with the tides. If you tire of tanning and swimming, climb well-marked trails into the surrounding mountains for spectacular views over the islands and sea.
This unparalleled setting has long inspired humankind to build, from today's pretty fishing villages to a ruined hermitage atop the island of Sandinderi, connected to the mainland at low tide.
Far more ancient remains include the Dolmen of Sorbituaga-Arriatara (Busturia), perhaps dating to the Iron Age, and the ancient paintings of Cave Santimamiñe. Surrounding this last are the Enchanted Forests of Oma, where artist Agustín Ibarrola works directly with nature.
By car, you can access the park from the region's main city of Guernica, at the junction of the BI-2238 west to Lequeitio, and BI-635, which runs along the Oca River's west bank toward the coastal fishing town of Bermeo; both cities and this portion of BI-635 (BI-2235) are located well within the reserve. The highway turns inland at Bermeo and runs toward Bilbao.
EuskoTren Line 3 Atxsuri (Bilbao) -Bermeo stops at the entrance to Urdaibai as well.