And of course ships! A lot of ships, because Greece has a lot of seasides! The total length of Greek coast is almost 13.676 km. It is almost half the total length of African coast! The earth tectonic plates of Asia and Africa are moving towards Europe and the connection point is Greece, so a lot of earthquakes gave the country many corners in geographical shapes.
Greeks specialized in making small but fast and easy to use boats. They had small ports so they had to use small ships! But they could travel at least from the Greek islands to Cyprus to carry copper and bronze since 3000 B.C.
The most famous ship was the trireme (first constructed by Corinthians close to 700 B.C.). It was almost 40 metres long and required almost 150 men power to pull the oars and almost 50 more for other needs.
If you take a look at: http://www.atm.ox.ac.uk/rowing/trireme.html you can find information about a reconstructed ship and where it is travelling today.
Homer in the Heliad described the first known organized navy, where 1186 ships floated to Troy. Homer describes a lot of details of these ships.
Some indications show that Greek ships had gone as far as England to buy metals that were hard to find in Greece.
In Spain, close to Gibraltar, there is a tower believed to have been built by Hercules. As the myth tells, there were two such towers to guide the ships to the passage of Gibraltar. This automatically means that some ships were daring to try the Atlantic Ocean!
Another source says that in Chile there are some people with roots to Ancient Sparta! A local professor collects a lot of amazing information about it!
The first war ships were armed with catapults! The tyrant of Syracuse Dionisios The Senior had ordered the improvement of the catapults that were available until then and managed to achieve superiority in the Mediterranean Sea in his period. He had constructed specially navigated ships that specialized in carrying catapults as war ships!
Today Greeks are following the traditions and have many more ships than someone would expect, considering the size of Greece. Unfortunately the Greek ship owners don't prefer Greek sailors any more. In 1980 we had 120.000 native sailors, now (1997) only 25.000.