I stayed right next to the Panathinaikos stadium in Ambelokipi during my trip to Athens a few years ago and I was shocked by how poorly it was maintained. Do they actually play/train there? I can't believe that one of the most prominent football clubs in Greece plays in such a shitty arena
Everytime there are plans to renovate it, it is blocked. It's a fucked up situation but if you don't bother you can see a basic description of the shitfest below.
Old management (from mid to late 2000s) essentially gave up the rights of having a proper permit there as they tied it in a stupid stadium project elsewhere so they have to renew the building license every five years just to not have it teared down.
The only reason why the football team plays at OAKA is because the guy who run the club (which owns the stadium) did not let the football team play there and wanted more money than what the Olympic stadium requested. Which is nuts.
The stadium itself hosts at least 15 other sports, from basketball ((women's and youth academies) to boxing, archery, table tennis, weight lifting, Olympic shooting and various others. It's not just football, there's a whole organization involved there daily.
The system in Greece is similar to the Spanish one, but in 1979 they decided to have a "professional" system so every team had to create a company that run the football part. The club owned the shares and by law has to own at least 10%. So essentially that meant that eventually 90% of the football team is owned by a third party and not the club itself, unlike Barcelona and Real Madrid for example where the club is owned exclusively by the club members or Germany with a 50+1 rule which leads to majority rule by the club members.
The situation is beyond shit with internal issues since 1996 that come and go (1996, 2000, 2004, 2008, 2012, 2016, 2020, seriously every four years there's another huge situation going on and it's usually for the worse) and general corruption in the league that drives people away from having an actual interest to get invested in this thing.
So fans want to rebuild a stadium where the current one is, government wants that piece of land for themselves (it's a huge plot in the center of Athens and its busiest intersection) and no one running the club has the guts to chase this because they are more interested in making money by being handed business opportunities in the new disastrous stadium project which keeps getting worse and worse and has become an even bigger financial burden for the long run than the current situation.
In Greece it's basically like in Italy. One club runs the system and even the country, has its own stadium which was built scandalously while AEK was supposed to be in the project and had its own stadium teared down in the early 2000s only to manage to rebuild it, well, next year! No one else has a new stadium. It's just Olympiakos. And ever since they built it in 2004, away fans have been banned in Greece, mostly because they don't want other fans to go there and make a mess of it.
If you want a new stadium, even when you own the land and have the money, you have to bend over to the government, city council, several judicial boards, political parties, several non-existent "social clubs" or "environmental clubs" and your own crazy management/ownership that doesn't align their interests with those of the club's prosperity.
Just consider than in 2008 a new stadium was blocked because 300 random people signed to preserve a place that is essentially an industrial dumpster, because some Athenian crows allegedly live there. Which became a funny meme when the political party that run that shit ended up being government and wanted to push that project again and the message was "the crows have left"
Funny thing is that there is a fund approved by the council to renovate it, but the same council doesn't give the relevant permits to do so
The main reason is because they fucked up with the building permits and the coefficients of building structure so you cannot do much. It's legally a "park" and not a building while it has a permit as a sports stadium and a valid license to be an actual sports related structure. Never go full Greek with the legalities
So long story short, those who have the power to fix this, don't give a fuck.