Eratosthenes measuring the circumference of earth

More than 2,000 years ago Eratosthenes compared the position of the Sun’s rays in two locations to calculate the spherical size of the Earth with reasonable accuracy.
 Eratosthenes was born in the Greek colony Cyrene, now the city of Shahhat, Libya. As a young man, he traveled to Athens to pursue his studies. He returned to Cyrene and made such a name for himself in scholarly endeavors that the Greek ruler of Egypt brought him to Alexandria to tutor his son. When the chief librarian of the famous Library of Alexandria died in 236 BCE, Eratosthenes was appointed to the prominent position around the age of 40.
A man of many talents, Eratosthenes was a librarian, geographer, mathematician, astronomer, historian, and poet. His friends at the library nicknamed him Pentathlos, or athlete who competes in five different events. The name seemed to fit a scholar who excelled in many fields of study. Most of Eratosthenes’s writings have been lost, but other scholars reported his work and findings — which were extensive.

Democritus atomic theory

Democritus (Stanford encyclopedia)

Talos the ancient robot

TALOS was a giant, bronze automoton--a living statue forged by the divine smith Hephaistos (Hephaestus). According to others he was instead the last of the ancient bronze race of man.
Zeus gave Talos to his lover Europa after delivering her to the island of Krete (Crete). The giant was given the task of patrolling the island and circled it three times a day, driving off pirates with volleys of rocks. He was eventually destroyed by Poeas or the Dioskouroi (Dioscuri) twins with the aid of the magic of the witch Medea as he tried to prevent the Argonauts from the landing on the island.

The death of Talos

The Lighthouse of Alexandria

Alexandria, Egypt was founded by Alexander the Great in April 331 BC ,and became the capital of the Graeco-Egyptian world. The second largest city in Egypt, Alexandria also was called "The Pearl of the Mediterranean". The ancient port city was home for one of the Seven Wonders of the Ancient World - The Pharos of Alexandria (The Lighthouse of Alexandria).
The port served as a primary center for commerce and trade linking Europe with the Middle East and all other points along the Mediterranean Sea. It was an important route for merchants and travelers of ancient times that allowed for trade and cultural exchange between emergent peoples of the region. Within a few generations Alexandria become the largest city in the world second only to Rome. Much of the city design and construction came under the rule of Ptolemy and his successors, later by the Roman Empire. The city was not only a center for trade but also became the worlds first center for cultural and scientific research.