Castle Cortewalle in the village of Beveren, East Flanders, is, like the windmill of Onze - Lieve - Vrouw - Lombeek, one of the places closest to the very heart of the Kapitein Zeppos series. It appeared in the first series, doubling for Belderbos Castle, the building at the centre of the estate that Captain Zeppos' late Uncle Nico had willed to him and his niece Ariane. In reality, the earliest buildings at Castle Cortewalle date back to the 15th Century, and the interiors were extensively renovated in the mid-1800s. Remarkably, in it's entire history, it was only ever owned by three families - Triest, Goubau and Brouchoven de Bergeyck - and unlike most other castles in the area, was never under attack or siege. Its greatest enemy would prove to be time and dereliction...

The castle is first shown in the fifth episode of the serial, De Geheimzinnige Kamer ("The Mysterious Room"), one of the most effective and memorable episodes of the whole series. It is seen both in the present day and the past, as a much younger Ben Kurrel explores it and finds the closed-off room. In both instances, the building is derelict and in a sorry state of repair. Any suspicions that the building had been 'dirtied up' for filming are quickly dispelled. It's clear to see that the building had seen better times. Two years after Kapitein Zeppos filmed there, the castle was placed under the care of the city of Beveren, and a renovation programme in the 1980s brought an incredible transformation to the estate.