The countryside around Estella is littered with monasteries. One of the best is the Monasterio de Irache, 3km southwest of Estella, near Ayegui. This ancient Benedictine monastery has a lovely 16th-century plateresque cloister and its Puerta Especiosa is decorated with delicate sculptures. Those unimpressed by beauty dedicated to God may find the Fuente de Vino (Fountain of Wine) enough to make them a believer. It's behind the Bodegas Irache, a well-known local wine producer (just in front of the church), and yes, it really is a free-flowing wine fountain, though you'll have to get there early since only 100 litres are released per day.
About 10km north of Estella, near Abárzuza, is the Monasterio de Iranzu. Originally founded way back in the 11th century, but recently restored, this sand-coloured monastery with beautiful cloisters is so calm and tranquil that it could inspire religious meditation in Lucifer himself.