From Stamps of the World
Bilthoven is a village in the Dutch province of Utrecht. It is a part of the municipality of De Bilt. It has a railway station with connections to Utrecht, Amersfoort and Baarn. It is home to the Netherlands National Institute for Public Health and the Environment, RIVM; and to the Union Mundial pro Interlingua, UMI, which promotes Interlingua internationally.
Read more @ https://en.wikipedia.org/wiki/Bilthoven