Hilversum

If you want to release 1000 toy balloons or more in the red-marked area, then you need to coordinate with the Airport Authority in advance. 

See http://www.ehhv.nl/contact and the AIP, part 3, EHHV, AD 2.2 'Aerodrome geographical and administrative data'.

Available daily between 07:00 and 17:00 (local time) for requests for special flights, activities, and events.