Yes indeed, to become a member of the Historic Conference Centres of Europe, the conference venue has to be able to look back on a past of over 100 years. This, however, does not imply that it is not allowed to have younger members in its family.
As far as congress|graz is concerned, the younger (but definitely not smaller) sister is Stadthalle|graz. Just this year, the fledgling of the Graz congress environment is celebrating its 10th anniversary. As is the case with all youngsters, it is very proud and wants to be properly acclaimed. It also enjoys sharing on Facebook with all its friends, where every month, fans have a chance to win 10 tickets for the most popular events of the year, and of course, you are invited to participate: www.facebook.com/mcggraz.