Home supporters give their side such encouragement that no opponent can expect an easy match
Celtic Park could never be described as a seething cauldron of hate. There has been no spectre of overt intimidation towards foreign opposition, be that by "Welcome to Hell" banners or otherwise. Yet there is clearly something about the atmosphere within Glasgow's east end on European nights that unnerves even top-class visiting teams.
What Celtic have occasionally lacked in talent when competing against foreign opponents they have made up for in feeding off the energy of their supporters. A vibrant atmosphere is one thing; using it to your advantage is quite another.
Juventus will arrive at Parkhead on Tuesday night having already suffered a defeat at the venue – 4-3 in 2001 – and therefore with first-hand knowledge of how strong Celtic can be with the roar of almost 60,000 punters ringing in their ears. Right back to the 1960s Celtic have demonstrated an ability to humble illustrious visitors. Manchester United, Barcelona, Real Madrid, Benfica and Milan are among those who have discovered this to their cost and in varying, often spectacular, circumstances.
Alan Thompson scored Celtic's winner in one of their victories over Barcelona and later formed part of Neil Lennon's coaching staff. Thompson and Lennon were both in the Celtic team, under Martin O'Neill, which made inroads for the club in Europe after a relative spell in the wilderness.
"Part of it, I think, is that the build-up to these matches always seems to go on for weeks so the supporters are really up for the games by the time they come around," says Thompson of Celtic's home European ties. "Then you have the supporters so close to the pitch. The acoustics of the stadium seem to work perfectly.
"The fans undoubtedly give the players a lift and have done at Celtic Park historically. Even if there are long spells where Celtic aren't in possession, the fans keep on backing the team. They are more patient than in domestic games, where there is almost an expectancy that Celtic should be two or three goals ahead. That is important, I think; the fans understand the context of these matches."
Neil Lennon agrees: "It is the only show in town, a European night at Celtic Park. For me it has one of the best atmospheres in world football, never mind European football."
That sentiment is not restricted to those associated with Celtic. Tito Vilanova, in charge of Barcelona when they lost in Glasgow last November, said: "I have been lucky in my career to have been to many grounds but I have never seen anything like it." Xavi added: "The stadium is a marvel" while Gerard Piqué claimed there were "no words to describe the atmosphere at Celtic Park". Sir Alex Ferguson and Ryan Giggs have been similarly effusive in the past.
Ominously for Juventus, Celtic have not lost at home to Serie A opponents since March 1969, when Milan departed with a 1-0 victory. If Thompson's thoughts are correct, the Italians cannot count even on the backdrop being punctured by a Celtic setback during the first 90 minutes of this last-16 tie.
On this tie the Celtic midfielder Kris Commons says: "It's a weird feeling. You try to stay as calm as possible and you get all this advice from people telling you not to let the crowd affect how you play but it's hard to do that.
"I'm 29 now and I think my experience has told me that you've just got to relax and concentrate on your own game and try to ignore the crowd. But when you are playing well you want to lift the crowd, take inspiration and put the pressure on Juventus."
Other players attempt likewise at different venues. Few of those stadia, though, can generate the electrifying, spine-tingling noise of Celtic Park when one of Europe's top sides are being hosted. Hampden Park, Scotland's national football stadium, shamefully lacks that verve.
"When that Champions League music starts up, the sense of anticipation and expectation just rises," says Celtic's goalkeeper Fraser Forster of the pre-match scene. Forster and his team-mates hope to thrive on that energy one more time to the cost of Juventus.