Sint-Geertruiabdij (St Gertrude's Abbey) is a medieval monastic complex on the north side of the old town, a short walk from the Grote Markt. The abbey was founded in the 11th century and became an important centre of the Augustinian Canons; the Gothic church, built mainly in the 15th century, survives in good condition and is one of the less-visited historic buildings in Leuven.
The church interior is worth entering for its carved choir stalls and the late Gothic vaulting of the nave. The abbey buildings around it have had a varied history — used as a barracks, a prison, and eventually restored to religious use. The complex is quieter than the central sights and attracts few tourists, which makes it a good choice if you want to see serious medieval architecture without the crowds. The church is usually accessible during the day; times vary by season.