3 Fonteinen Open Beer Days
From Lambic.Info
Overview
3 Fonteinen Open Brew Days is a festival put on the by the brewery in which the brewery is open to the public for free tours. There is food, drink, music, tours, and activities. Guests are able to purchase vintage or otherwise unavailable bottles at the brewery's in-house shop.
The Open Brew Days event generally happens around the first weekend in September.
This video (dutch) was shot during Open Brew Days, 2013: http://deredactie.be/cm/vrtnieuws/videozone/programmas/terzake/2.29937?video=1.1723181 (the coverage starts at 1:50)