The Château d'Arenberg is a Flemish Renaissance castle in the Heverlee suburb, now part of KU Leuven's Arenberg science campus. Built in the 16th century for the noble Arenberg family, it was acquired by the university in the 20th century and now serves as an administrative building. The castle and its grounds are open to the public — the university campus that surrounds it has spread considerably, but the castle itself retains its moat and towers and looks much as it did in historical engravings.
The Arenberg campus is an interesting contrast to the historic city centre: a mix of Victorian-era engineering buildings, modernist science facilities, and the Renaissance castle at its heart, set in extensive landscaped grounds. It's about 2 km from the centre, reachable by bike along pleasant paths. On sunny days the grounds around the castle and the adjacent Arenberg Park fill with students and families. The combination of the château, Park Abbey, and the surrounding woodlands makes the southern approach to Leuven worth half a day.