It can get moderately busy during peak tourist season (July-August) and on sunny weekends, but rarely overcrowded.
The 'Old Middelburg Cathedral' (encompassing the Middelburg Abbey complex) experiences varying levels of busyness. During the peak tourist season, typically July and August, and on sunny weekends, it can get moderately busy, especially around the Lange Jan tower entrance and in the main abbey courtyard. Middelburg is a popular destination, and the abbey is a central attraction.
However, it rarely becomes excessively overcrowded like some larger European landmarks. Outside of peak season, particularly on weekdays, the complex is much quieter, offering a more serene environment. Weekday mornings are generally the least busy times. While you might encounter groups, it's usually possible to explore without feeling overwhelmed by crowds.