Eat pintxos (small tapas)

Walk to Getaria (next town to the west from Zarautz) has open grilled, small bars and best seafood

Day trip to San Sebastian - both train and bus depart from Zarautz regularly

Day trip to Bilbao - catch the bus from Zarautz

Lots of hiking

Zarautz San Pelaio festival (26th-28th June)