Darius I revolutionizes the economy by placing it on a system of silver and gold coinage.

Trade is extensive, and under the Achaemenians an efficient infrastructure facilitates the exchange of commodities among the far reaches of the empire.

As a result of this commercial activity, Persian words for typical items of trade become prevalent throughout the Middle East and will eventually enter the English language; examples include asparagus, bazaar, lemon, melon, orange, peach, sash, shawl, spinach, tiara, and turquoise.

Trade is one of the empire's main sources of revenue, along with agriculture and tribute.

Other accomplishments of Darius's reign include  codification of the data, a universal legal system upon which much of later Iranian law will be based, and construction of a new capital at Persepolis, where vassal states offer their yearly tribute at the festival celebrating the spring equinox.

In its art and architecture, Persepolis reflects Darius's perception of himself as the leader of conglomerates of people to whom he has given a new, single identity.

The Achaemenian art and architecture found here is at once distinctive and highly eclectic.

The Achaemenians take the art forms and the cultural and religious traditions of many of the ancient Middle Eastern peoples and combine them into a single form.

This Achaemenian artistic style is evident in the iconography of Persepolis, which celebrates the king and the office of the monarch.

A great patron of the arts, Darius initiates construction on a complex of palaces and buildings at the royal complex of Persepolis (near modern Shiraz in southwestern Iran) around 518 BCE.

Located about fifty miles (eighty kilometers) south of Pasargadae, Persepolis, as was also typical of Assyrian palace complexes, is constructed atop a huge limestone platform that serves to level off the site and provide a secure foundation for its structures.

Darius, after becoming aware of the Persian defeat at the Battle of Marathon, begins planning another expedition against the Greek-city states; this time, he, not Datis, will command the imperial armies.

Preparations for a third Persian expedition are delayed by an insurrection in Egypt, and Darius dies in 486 BCE before they are completed.

The thirty-six-year-old crown prince, a younger son of King Darius by Atossa, sister-widow of the late Cambyses and daughter of Cyrus the Great, inherits the throne in October or December of this year as Xerxes I (Persian: “Khshayarsha”), meaning "ruler over heroes."

Darius the Great is certainly a great builder and an even greater administrator than his illustrious predecessor Cyrus the Great, completing the organization of the empire into satrapies and fixing the annual tribute due from each province.

He has standardized coinage, weights, and measures and developed and land and sea routes undertaken to promote imperial trade and commerce.

Darius, a probable Zoroastrian who apparently promotes the religion in Persia, has followed Cyrus’s example in respecting native religious institutions, empowering the Judahites to rebuild their Temple at Jerusalem and actively supporting Egyptian religion.

Assuming an Egyptian titulary in Egypt, he has built a temple to the god Amon in the Kharga oasis, endowed the temple at Edfu, and initiated restoration work in other sanctuaries.

Darius has also authorized the Egyptians to reestablish the medical school of the temple of Sais, and has ordered his satrap to codify the Egyptian laws in consultation with the native priests.

Darius’ death has left to his son the task of punishing the Athenians, Naxians, and Eretrians for their interference in the Ionian Revolt, the burning of Sardis and their victory over the Persians at Marathon.

From 483 BCE, Xerxes had begun preparing his expedition: A channel is dug through the isthmus of the peninsula of Mount Athos, provisions are stored in the stations on the road through Thrace, two pontoon bridges later known as Xerxes' Pontoon Bridges are built across the Hellespont.

Soldiers of many nationalities serve in the armies of Xerxes, including the Assyrians, Phoenicians, Babylonians, Egyptians and Judahites.

Among the Phoenician naval contingents of the Persian fleet are the sailors of Sidon.

Xerxes concludes an alliance with Carthage, and thus deprives Greece of the support of the powerful monarchs of Syracuse and Akragas.

Many smaller Greek states, moreover, take the side of the Persians, especially Thessaly, Thebes and Argos.

Xerxes returns to Persia after the military blunders in Greece, and completes the many construction projects left unfinished by his father at Susa and Persepolis.

He builds the Gate of all Nations and the Hall of a Hundred Columns at Persepolis, which are the largest and most imposing structures of the palace.

He completes the Apadana, the Palace of Darius and the Treasury all started by Darius as well as building his own palace which is twice the size of his father's.

His taste in architecture is similar to that of Darius, though on an even more gigantic scale.

He also maintains the Royal Road built by his father, …

…completes the Susa Gate and builds a palace at Susa.

Sataspes, a Persian navigator and cavalry commander—who, according to Herodotus, was Xerxes I's cousin by his mother being Darius I's sister—had been condemned to death for kidnapping and raping Megabyzus's daughter.

However his mother, Atossa, had successfully persuaded Xerxes to change the punishment to a more severe one—Sataspes was tasked to circumnavigate Africa.

He took an Egyptian ship and crew, sailed through the Pillars of Hercules, and proceeded south for many months, but returned to Egypt without successfully completing his task.

He claimed that at the farthest point he reached, he encountered a "dwarfish race, who wore a dress made from the palm tree", and that he was forced to return because his ship stopped and would not sail any further.

Xerxes did not accept this excuse, and had him put to death.

However, it has been suggested that Sataspes could have simply encountered the Benguela Current, the broad, northward flowing ocean current off southwest Africa, which prevented him from sailing any farther.