If you are really looking for a way to get to Athens - Kalamata then I can suggest 3 options: by bus, car or plane. These are the best options, but I will say that flying by plane will be the fastest and most comfortable way. Kalamata has an international airport located 7 km from the city. This is the closest airport to the resorts of Peloponnese. I learned all this here - https://aktis.blog/en/athens-kalamata-how-to-get-there
If you are really looking for a way to get to Athens - Kalamata then I can suggest 3 options: by bus, car or plane. These are the best options, but I will say that flying by plane will be the fastest and most comfortable way. Kalamata has an international airport located 7 km from the city. This is the closest airport to the resorts of Peloponnese. I learned all this here - https://aktis.blog/en/athens-kalamata-how-to-get-there