[8] It had been believed that the European Commission were investigating this use of public funds for any possible impropriety in the deal, but in late 2013 it was confirmed by Joaquín Almunia, the commissioner for competition at the time (and an Athletic supporter from Bilbao), that no such case was being pursued.

As the new stadium was not quite ready, their opening game of the campaign (a 2–0 win over Osasuna) was played at Anoeta in Donostia-San Sebastián, home of rivals Real Sociedad.

Towards the end of the 2015–16 season, throughout the summer break and at the outset of 2016–17, extensions were added to the roof at a cost (borne solely by the club) of €12.6 million, estimated to increase the effectiveness against wet weather by 70%.

[18][19] The lack of sunlight onto the pitch from the roof is offset by internal lighting modules which maintain the condition and growth of the turf, a system used in other Spanish stadiums.

[21] The stadium is equipped with a sophisticated lighting system on its exterior which can be programmed to illuminate the hundreds of panels on its facade (which by day are white) in solid colours, or to show flashing or moving graphics (such as when a goal is scored, or the UEFA Champions League star-ball motif when Athletic qualified for that competition).

[24] It looks onto the Pozas, a street running to the stadium from the heart of the city which is a popular walking route for fans on matchdays and is lined with Athletic-themed bars.

It is a club tradition for captains of teams visiting the Athletic ground for the first time pay homage to the fallen idol of its early years, Pichichi, by leaving a bouquet of flowers at a bust of the player.

Despite concerns that this iconic feature might not be accommodated at the new stadium,[25] a suitable spot was identified at the entrance to the players' tunnel, allowing the tradition to continue at the new location from 2013 onwards.

[32] As part of the club's 125th anniversary celebrations in 2023, a subtle feature was unveiled in the open space outside the stadium depicting the exact placement of the goal lines of the old pitch,[33] followed later by a statue of the appearance record holder José Ángel Iribar.

A 'beam back' event was held at the stadium in May 2015 for the 2015 Copa del Rey final for fans who could not attend the game in Barcelona, with giant video screens installed on the pitch that the spectators could view from the stands.

[36] In 2017, there was a realistic possibility that the stadium could host the Copa del Rey final for the first time after Deportivo Alavés from nearby Vitoria-Gasteiz qualified for the showpiece game to face FC Barcelona.

[46] However, ultimately San Mamés was replaced by La Cartuja in Seville due to the COVID-19 pandemic in Spain, with infection rates higher in the Basque Country than in Andalusia at the time of making final arrangements for the tournament in April 2021.