The Stoop Pavilion

The Stoop Dome was built on behalf of the Amsterdam banker J.B. Stoop in 1840. The pillars come from the former Koopmansbeurs in Amsterdam, which was demolished in 1836. The dome used to serve as a tea house and today as a studio (visitable by appointment only).

Since 1826, the banker  J.B. Stoop owner of the moors south of the current N224. He had the heathland wooded and asked landscape gardener J.D. Zocher to construct a country estate on a high point with a panoramic view: the De Hoogt estate. In 1840 he had a tea cupola built by Zocher and started to lay out a landscape park containing the never-finished house De Hoogt (not to be confused with the later Huis De Hoogt near Maarn) and a hunting lodge, the current Berghuis. However, because it turned out to be impossible to build a pond due to the low groundwater level, he abandoned his further plans. In 1849 Stoop bought another location in Zeist and had the Molenbosch house built there. The dome on the Henschoten estate went down in history as the Dome of Stoop.
Source and more info: Wikipedia

You don't expect to find it in the middle of the forest