El Vallès Occidental still has some small olive farms, mainly in Castellar del Vallès, Ullastrell and Castellbisbal.
A preference for local produce has become widespread over recent years and their production and local character are increasingly valued.
The Ullastrell cooperative, founded in 1939, maintains the only oil mill in the county covered by regulations and makes extra virgin olive oil with Becaruda and Arbequina olives grown in the municipality.
The Moli d’Ullastrell can be visited by appointment in late November, December and January.
The Ullastrell Festa de l’Oli (Oil Festival) is held in the first fortnight of January and features a range of activities based around this treasured product.