O.A.C.A. Olympic Indoor Hall

The Nikos Galis (since 2016) Olympic Indoor Hall of O.A.C.A. is a part of the Spyros Louis Olympic Athletic Center of Athens (O.A.K.A. «Σπύρος Λούης»), was completed in 1994 and is the largest indoor venue in Greece. It was used for sporting events at the 2004 Summer Olympics. The venue is located in Marousi, in the northern section of Athens. During its construction, it was considered to be one of the biggest and most modern indoor sports arenas in all of Europe.

The 18,300-capacity arena also contains a training facility. Since 2016, it has been named after the Greek basketball player Nikos Galis.

In 2023, Panathinaikos B.C. signed an agreement with the Greek state for a 49-year concession of the venue, making the club the sole tenant and binding it to invest in the renovation of the asset's infrastructure.

Construction
Nikos Galis Olympic Indoor Hall is notable for its distinctive A-frame roof that features four huge pillars, each of which is 35 meters tall, that stand 108 meters apart from each other. According to the Greek Ministry of Sports, it is the largest indoor sporting arena of its kind in the world. The arena is also constructed in a unique way so that an abundant amount of natural light comes into the arena during the day.

The arena seats up to 17,600 for gymnastics events, although only 12,500 seats were made publicly available for the gymnastics competition at the 2004 Olympics. It seats up to 19,443 for basketball games, which includes 300 seats for media members, and 189 seats for VIPs.

A large scale arena renovation was completed in 2004, for the 2004 Summer Olympics.

2004 Summer Olympics
The arena was used for artistic gymnastics and trampolining, and also hosted the finals of the basketball matches at the 2004 Summer Olympics. Renovation of the building for the Olympics was completed on 30 June 2004, and it was officially reopened on 10 August 2004, shortly before the beginning of the games.

Basketball use
The Indoor Hall is the regular home court for the Greek Basket League professional basketball club Panathinaikos. It is also the primary home court of the senior Greek National Basketball Team.

The arena was used to host the quarterfinals, semifinals, and finals stages of the 1998 FIBA World Championship.

On 4 and 6 May 2007, the Indoor Hall hosted the EuroLeague 2006–07 season's Final Four, the semifinals and finals rounds of Europe's principal pro club competition in basketball, which saw hometown favourite Panathinaikos win the title.

On 9 December 2007, FIBA announced that the Olympic Indoor Hall was selected as the host of the 2008 FIBA Olympic Qualifying Tournament for the 2008 Summer Olympic Games. At the qualifying tournament, hosts and favourites Greece, along with the German and Croatian national basketball teams, qualified for the final 2008 Olympic Basketball Tournament.

Musical events
On 18 and 20 May 2006, the Hall hosted the 51st Eurovision Song Contest, that was held in Athens, after Greece's victory at the Song Contest in 2005. There were 15,000 seats available for spectators, both for the semifinal and the grand final.

Some of the entertainers who have performed at the arena include Maluma,Slayer,Rotting Christ, Pearl Jam, Enrique Iglesias, Depeche Mode, Jennifer Lopez, Björk, Beyoncé, Slayer, Roger Waters, Aloha from Hell, Tokio Hotel, Helena Paparizou, Sakis Rouvas and Anna Vissi.