However, lately, works have been done on the treatment and cleaning of water resulting in an outstanding environmental recovery.

The phenomenon looks similar to tidal bores, but it's caused by ocean swells instead of tides.

Similar to tidal bores, the waves form in the ocean and travel up the river.

[3] The current water quality allows for a stable fish fauna with five species populating the river, namely salmon (extinct in 1940 and restored thanks to the re-population programs of the 1980s), trout, common minnow, loach and eel.

); Astigarraga, renowned for its cider houses; and Donostia with a final long stretch of the river snaking through different parts of the town.