The second largest European IT-related conference is FOSDEM (5000 participants); of course it has a different focus. But it's more productivity, less party. Th

The second largest European IT-related conference is FOSDEM (5000 participants); of course it has a different focus. But it's more productivity, less party. Then there are conferences like HITB Sec Conf that are much smaller, but focus exclusively on security - many (probably most) Congress attendees don't really have a security/hacking background, so I'm not sure the total number of attendees is a good metric for "is it a good security conference?". Though Congress does get all the high-profile talks. And there is no European hacker conference with nearly as much visibility as C3.