Lisbon has a special place in the minds and hearts of Celtic supporters, for obvious reasons. It was there that the club recorded the greatest success in their history, beating Inter 2-1 to win the European Cup in 1967, becoming the first British club to do so.
Yet more recently, things haven't been quite so memorable when Celtic have had to travel to the Portuguese capital. In their past two Champions League outings away to Benfica, Celtic have lost 1-0 and 3-0 and while a defeat tonight wouldn't kill their chances of qualification, it would put them in a far from ideal position.
Here are five key aspects of the game which could prove decisive if Celtic are to continue their impressive Champions League form tonight.
Too often in the Champions League, away from home anyway, a lacklustre start, often leading to an early goal, has cost Celtic dearly.
And it's happened before against Benfica.
No sooner has the game started than they find themselves behind, and with the mental pressure of their poor European away record weighing down on them, the task is uphill from there.
This year however, in both of their away matches in the group Celtic have taken the early advantage, leading to a victory in Moscow against Spartak and only the narrowest of defeats against Barcelona.
If Celtic are able to score first tonight in Lisbon, they give themselves a great chance of getting a result.
Benfica will look to keep possession and probe at Celtic looking for the chance to make something happen—much as they did earlier in the campaign at Parkhead.
Jorge Jesus may have lost Javi Garcia to Manchester City just before the transfer window closed at the end of August, and Pablo Aimar is missing through injury, but Benfica still pose a threat and Celtic will be looking to ensure that their midfielders and forwards drop deeper in order to close down and reduce the space available to the home side.
It never seems the most flattering thing to say about a side, but much of Celtic's success so far this season has been down to their set pieces and their ability to create opportunities by putting an accurate ball into the box.
Two of their goals over the two games against Barcelona came from Charlie Mulgrew deliveries (a free kick and a corner) and all three of their goals against Spartak Moscow came from crosses from wide positions.
Neil Lennon will be looking to his left foot to cause similar problems tonight.
Mulgrew will have plenty of targets to aim at as well, with the likes of Wanyama, Ambrose, Lustig, Samaras and Wilson all dangerous in the air.
While Celtic's success tonight will hinge on a combined team effort, the work rate, composure and intelligence of Samaras could prove invaluable.
His ability to hold onto the ball, bring other players into the game and create chances even when isolated and with little support make him essentially the first name on the team sheet for European away games.
Much has been made of the possession statistics from Celtic's previous two Champions League encounters, with some crediting them with as little as 10 percent of the ball, but it's always that much more complicated playing against a side like Barcelona.
In Moscow the story was quite different and the fact that Celtic were able to keep the ball and move it around was a big factor in being able to go out and get the victory.
They now have a midfield capable of playing this way in Europe, both at home and on their travels and they've found just how big a difference it can make.