The artist Agustín Ibarrola has created an unusual work of art by painting striking designs on a swath of trees inside the Urdaibai Biosphere Reserve. A 7km loop trail takes you through a serene forest of pine, sun-dappled ferns and fragrant eucalyptus, with the enigmatic works hidden within.
It's located 6.5km northeast of Gernika. Follow directions to the Cuevas de Santimamiñe, which is just across the road from the starting point to the Bosque Pintado de Oma.