European Union: The Greek Parliament ratified the Act of Accession on 28 June 1979, and Greece became the tenth Member State of the European Community on 1st of January 1981.

Language: The official language in Greece is Greek language (native name: ελληνικά).

Currency: Greece is one of the 19 states member that has EURO currency.

Card Payments and Cash Withdrawals: 
You can pay with international credit cards everywhere, starting from 1€. 
You might struggle to find places that accept American Express around the small islands. Some cash is good to have on you.
ATM: Athens has ATMs from banks but also private ATMs that will overcharge you. On the islands, you can find only private ATMs (for 100€ the fee is like 2.5€).

Connexion: The Internet is very good on the continent. On the islands, it depends. I struggled a lot with Zante, for instance. Wi-Fi connection almost everywhere you go, free or on demand in some restaurants or hotels. But … the connexion is not that good.

If you are from the EU, roaming is free of charge. You can call and connect to your mobile data as if you were in your country of origin without extra costs.

Railroads: You will have connections through the continent and connecting other important cities in Europe. For the islands, boats or airplanes are the only options. If you take the place, please note you will not have a direct flight from one island to another. They will all gather at the hub in Athens where you will switch either the place or the company.

Plugs: Plugs are Type C and F. The standard voltage is 230V, and the standard frequency is 50Hz.