From the early years, Baron Etienne and Baroness Hélène surrounded themselves with wealthy friends. Nobility, but also new rich people, bankers, industrialists, artists and writers. Guests of royal blood also came to the castle. They can be found in the guest book. Queen Emma visited De Haar in 1901.

The castle complex has some 200 rooms, including more than 25 baths. It takes a lot to get the castle ready for the arrival of the family and guests. The whole castle is turned upside down. In the early years, around 1900, even horses, carriages and automobiles are transported from Paris to the Netherlands.

During August, additional reinforcements will arrive. Chambermaids, waiters, drivers, the butler, the kitchen crew, etc. The cooks usually come first. They start preparing, setting up the kitchen, drawing broths. Then in the castle also begins to smell of food and the castle suddenly takes on a homely atmosphere.

The Baron takes his role as Grand Seigneur very seriously; he has a day job. At the beginning of the twentieth century, every newspaper has a kind of society column: the "Chronique Mondaine. Those sections described how the aristocracy and Beau Monde were enjoying themselves. The baron - or rather his secretary - keeps entire scrapbooks of those sections, copying menu ideas and names: "Quelques noms pour invitations."

Now it is Baron Thierry's five daughters and granddaughters who are able to continue the tradition. Although the family no longer owns the castle, they have retained the right to stay here one month a year. The ownership of the castle and the park was transferred to Stichting Kasteel de Haar in the year 2000. This foundation aims to preserve the castle and open it to the public.