, a city which has dominated the competition in recent years.
Real Madrid have lifted the trophy in four of the past five seasons – and the past three in succession – while city rivals Atletico have appeared in two of the past five finals.
But, after a summer of sizeable change – at Real in particular, is this the year when their monopoly on Europe’s biggest club prize is ended?
We take a look at some of this year’s key Champions League talking points.
Is this the most open CL in years?
Real Madrid’s dominance of the Champions League in recent years reached unprecedented levels last season, when they became the first team to win the competition three times in a row.
No side had even managed back-to-back successes in the competition’s current format before Real achieved it in 2017.
That hat-trick of titles came under manager Zinedine Zidane, and with Cristiano Ronaldo as the central on-field character. Both have since departed the Bernabeu.
Football analysts Gracenote assess every team’s chances of winning the trophy using their Euro Club Index and, for the first time in three seasons, Real do not start the competition as the most likely winners.
In fact, Gracenote say the Spanish giants’ chances of winning have dropped from 30% at the start of 2017-18 to 19.4% this season.
The data also suggests there is now a larger pool of potential champions. Twelve months ago, there was a 69.4% chance of the winner being one of Real, Barcelona or Bayern Munich, whereas that figure now stands at 59.5%.
So who has the best chance of winning this season?
Are Real noticeably weaker without Ronaldo?
Spanish football expert Guillem Balague
The real question now Ronaldo has gone is whether Real have that ‘get out of jail free’ card that he brought to the table.
The individual quality is there, and manager Julen Lopetegui has added more control and more passing, which can easily mix with their usual and lethal counter-attacking game.
That mix of styles suits striker Karim Benzema – it will give him more responsibility, more touches of the ball, and more shots at goal. He has already scored five goals in as many appearances this season.
And Gareth Bale, who demanded a bigger role, is now able to fill in a lot of the spaces previously occupied by Ronaldo.
But the concern lingers: will they have that extra factor Ronaldo gave them? Although he did not score in last year’s semi-finals and final he has made the difference so many times over the years.
Ultimately, a player who was directly involved in exactly 50% of Real’s goals in the Champions League from 2009-10 to 2017-18 (105 goals, 27 assists) could well be missed when it really counts.
Did you know? Real are playing in the Champions League for the 22nd consecutive season, the longest run in the history of the competition. They have always made it out of the group stages, reaching the semi-finals in the past eight seasons.
With Ronaldo on board, is this the year Juve make that final step?
Italian football expert Mina Rzouki
Juventus have won Serie A seven years in a row, the domestic double for four consecutive seasons and reached the Champions League final twice in four years, only to be torn to shreds by the Spanish opponents they faced.
Their tactics always versatile, their squad united, the only problem manager Massimiliano Allegri pointed to was that Juve, unlike Barcelona and Real Madrid, did not boast a world-class difference-maker to win in Europe.
Cue the arrival of Ballon d’Or holder Ronaldo.