One of the biggest mistakes I've made traveling to different countries is not checking the visa requirements. This is especially important if you plan on staying in Greece for a very long time or if you have a passport that's not from a Schengen country, or the US, Canada, and Australia. Some countries that require a visa include China, Egypt, Lebanon and Russia. For a complete list, see this official Greek gov website https://www.mfa.gr/en/visas/visas-f...ountries-requiring-or-not-requiring-visa.html