The "Baile de la Alpargata" is a traditional dance in the Casino Principal (above Cafe Iruña) on the main Plaza del Castillo which takes place every morning at 9:00am.  However, the room only holds a few hundred spectators, so to get entrance is a bit tricky. 

The "alpargata" is a typical shoe from Navarra - a comfortable and cheap cloth slipper that can be purchased at many locations (especially calle Zapateria).