Those who visit Castle de Haar walk under no less than three gates, each accompanied by two towers. The first gate is at the entrance to the Stable Square. The third is the Pigeon Gate, which gives access to the Great Cour. In between is a gate between two square towers. This gate, together with two large wings, forms a complete little castle: the Châtelet.

Construction of the Châtelet begins in 1893 to the design of Joseph (Jos) Cuypers, son of architect Pierre Cuypers. The plans are frequently altered, as foundation work encounters old wall remnants. In addition, the new walls soon begin to sag. The final result is a graceful castle with many corners, bay windows, turrets and stairs.

The history of the Châtelet is complicated. This can be seen in its many level changes and numerous unexpected steps and passages. Like the great castle, the Châtelet has been adapted to the demands of modern times. It is an amazing combination of medieval forms and the luxury of the pre-World War I period.

The Châtelet or gatehouse is the main outbuilding of Castle de Haar. It is not really small; it is larger than many Dutch castles. Originally it was mainly intended as a shelter for installations: boilers, pumps, water and ice cellars, storage space.

In addition, this building will serve as a service apartment for the steward, machinist and other staff. In addition, there will be some extra guest rooms for guests. Later around 1910, there will be apartments for the sons (Helin, 1888-1912) and Egmont (1890-1960) of Baron Etienne and Baroness Hélène.

Starting in the 1950s, the Van Zuylen van Nijevelt family used the Châtelet as a family home. This was more intimate and practical. The large castle was only used in September to receive guests. Today, the family of Baron Thierry also lives in the Châtelet when they are in the Netherlands. This is at least three times a year: in summer, in autumn and at Christmas. Even now that Thierry van Zuylen (1932-2011) has passed away, his children and grandchildren feel very attached to their Dutch family home.

During the major restoration of Castle de Haar and its outbuildings (2001 to 2011), one building had been skipped: the gatehouse or Châtelet. There was no more money available for it. In 2012, thanks to a 'canjersubsidie' from the state, plus contributions from the province of Utrecht and some funds, the necessary 3 million euros came together. It was high time, because the Châtelet was beginning to become dilapidated.

Restoring a building like the Châtelet involved a lot of work. For example, 60,000 slates on the building's roof had to be replaced. In addition, all 2,000 parts of the windows and frames were taken down, de-rusted, repaired, treated and put back in place. Also, 5,000 handmade monastic bricks (large stones) were mortared into the facade and 13,000 kg of shell lime mortar was used to mortar and grout the facades.