The country estate Oud-Poelgeest (officially Kasteel Oud-Poelgeest) was built in 1668 in the Dutch Neoclassical style on the foundations of the medieval castle Alkemade. This castle was destroyed by Spanish troops in 1574.

The well-known humanist and physician Herman Boerhaave lived here between 1724 and 1738. He grew plants at Oud-Poelgeest for which there was no room in the botanical garden of Leiden University.

In the 19th century, four towers were built on the square house - making it look more like a castle - along with the coach house. The grounds also contain a gardener's house, a neo-Gothic chapel and a well dating from 1550. These building and the surrounding park are protected as a Dutch national monument.

Today, the coach house is a hotel-restaurant. The castle is used as a conference centre