37°39′07″N 24°01′34″E / 37.652°N 24.026°E
Cape Sounion (Modern Greek: Aκρωτήριο Σούνιο Akrotírio Soúnio [akroˈtirʝo ˈsuɲo]; Ancient Greek: Ἄκρον Σούνιον Άkron Soúnion, latinized Sunium; Venetian: Capo Colonne "Cape of Columns") is the promontory at the southernmost tip of the Attica peninsula, 8 kilometres (5.0 mi) south of the town of Lavrio (ancient Thoricus), and 69.5 km (43.1 miles) southeast of Athens in the Athens Riviera. It is part of Lavreotiki municipality, East Attica, Greece.
Lavrio, Lavrion or Laurium (Greek: Λαύριο; Ancient Greek: Λαύρειον (later Λαύριον); from Middle Ages until 1908: Εργαστήρια Ergastiria) is a town in southeastern part of Attica, Greece. It is part of Athens metropolitan area and the seat of the municipality of Lavreotiki. Laurium was famous in Classical antiquity for its silver mines, which was one of the chief sources of revenue of the Athenian state. The metallic silver was mainly used for coinage. The Archaeological Museum of Lavrion shows much of the story of these mines.
It is located about 60 km SE of Athens city center, SE of Keratea and N of Cape Sounio. Laurium is situated on a bay overlooking the island of Makronisos (ancient times: Helena) in the east. The port is in the middle and gridded streets cover the residential area of Lavrio. GR-89 runs through Lavrio and ends south in Sounio.
Theaetetus of Athens (/ˌθiːɪˈtiːtəs/; Ancient Greek: Θεαίτητος Theaítētos; c. 417 – c. 369 BCE), possibly the son of Euphronius of the Athenian deme Sunium, was a Greek mathematician. His principal contributions were on irrational lengths, which was included in Book X of Euclid's Elements and proving that there are precisely five regular convex polyhedra. A friend of Socrates and Plato, he is the central character in Plato's eponymous Socratic dialogue.
Theaetetus, like Plato, was a student of the Greek mathematician Theodorus of Cyrene. Cyrene was a prosperous Greek colony on the coast of North Africa, in what is now Libya, on the eastern end of the Gulf of Sidra. Theodorus had explored the theory of incommensurable quantities, and Theaetetus continued those studies with great enthusiasm; specifically, he classified various forms of irrational numbers according to the way they are expressed as square roots. This theory is presented in great detail in Book X of Euclid's Elements.