The O.A.C.A. Olympic Indoor Hall, which is a part of the Olympic Athletic Center of Athens «Spyros Louis», was completed in 1995, and was the largest indoor venue in use for sporting events at the 2004 Summer Olympics in Athens, Greece. It is located in Marousi, Athens. It is considered to be one of the biggest and most modern indoor sports arenas in all of Europe.
The 19,250-capacity arena also contains a training facility. Since 2016, it is named after the well-known Greek former basketball player Nikos Galis.
Wikipedia https://en.wikipedia.org/wiki/O.A.C.A._Olympic_Indoor_Hall
Address Μαρούσι 15123, Greece
Coordinates 38°2'16.058" N 23°47'4.961" E