And for those present, just shy of 10,000, it was a night they will surely remember for a lifetime.
As recently as four years ago, Iceland was ranked 133rd in the world but it now sits inside the top 35.
Faced with the daunting prospect of overcoming a team full of household names, including three-time World Player of the Year Cristiano Ronaldo, it recorded an historic point in its first ever appearance at a major international tournament.
But Iceland has overcome the odds to even reach this stage; with its outdoor pitches being unplayable for the majority of the year and with a population the same size as Leicester — less than 330,000.
Far from being overawed by the occasion, the minnows came out fighting. With the game less than three minutes old, Iceland almost took a surprise lead.
Gylfi Sigurdsson’s subtle feint took him past veteran defender Ricardo Carvalho, but the Swansea star tried to beat Rui Patricio at his near post and only contrived to shoot straight at the Portugal keeper.
But it didn’t take long for Ronaldo and co. to exert their dominance on the match. First, Vieirinha’s swerving strike stung the hands of Iceland keeper Hannes Thor Halldorsson, before Nani and Ronaldo both fluffed gilt-edged chances.
However, just after the half hour mark, Portugal finally took the lead. A wonderful, flowing move culminated in Andre Gomes squaring the ball for Nani to calmly divert past Halldorsson.
Portugal then started the second half as they ended the first and Ronaldo’s half-volley had Halldorsson scampering across his goal.
But then, five minutes into the second half, Iceland began re-writing the script.
Portugal’s makeshift full-back Vieirinha was caught out of position and Johann Berg Gudmundsson’s pinpoint cross was expertly swept home by Birkir Bjarnason.
In truth, either side could have stolen the three points. Ronaldo was guilty of heading straight at Halldorsson when free inside the six-yard box, before Iceland substitute Alfred Finnbogason saw his shot saved by Rui Patricio.
Portugal dominated throughout the three minutes of additional time but Iceland held on for a point that will surely go down in Nordic folklore.
In Tuesday’s early match, it was a day of re-writing history for Hungary.
The country’s first win at a European Championship since 1964; its first goal since 1972 and the oldest player to ever appear in the tournament — 40-year-old veteran goalkeeper Gabor Kiraly.
From 1950 until the Hungarian Revolution in 1956, Hungary’s team — dubbed the “Magnificent Magyars” — won 42 games, drew seven and lost just once — in the World Cup final against West Germany.
But Hungary then fell on hard times. It hasn’t been to a World Cup since 1986 and Euro 2016 ends a run of 44 years without a European Championship appearance.
With Austria boasting star names such as Bayern Munich’s David Alaba and the Premier League’s Marko Arnautovic, many didn’t give Hungary a chance prior to kick off.
And that analysis looked well founded as Austria started on the front foot, Alaba crashing a swerving 20-yard strike off the bottom of Kiraly’s post inside 60 seconds.
The Austrians continued to exert their dominance and a wonderful, flowing counter-attack — instigated by Arnautovic’s sumptuous flick — ended with the Stoke forward miscuing his pass into Martin Harnik’s path.
Hungary began to get a foothold in the game at the start of the second half and unexpectedly took the lead with its first real chance.
Without a goal in 41 games for club and country, Adam Szalai played a neat one-two on the edge of the box and calmly slotted the ball past goalkeeper Robert Almer, sending those Hungarian fans behind that goal into raptures.
Less than five minutes later, Austria thought it had equalized but the referee disallowed Arnautovic’s strike and proceeded to send off Aleksandar Dragovic for his second bookable offense.
Despite their numerical disadvantage, Austria began to lay siege to Kiraly’s goal.
However, with Alaba and co. frustrated and unable to make the breakthrough, a slick Hungarian counter finished with Zoltán Stieber deftly chipping the ball over the onrushing Almer to seal a historic win.