WASHINGTON -- It's about the size of a football and made of clay. It's chipped, cracked and is even missing a chunk.

But the Cyrus Cylinder is one of the most important pieces of pottery in history. On loan from the British Museum, it is on display in a small two-room exhibit at the Arthur M. Sackler Gallery in Washington, D.C., through April 28.

The lines of decoration are actually cuneiform, an ancient writing system, and they proclaim a different style of ruling -- one that says, "This is an empire that is going to recognize different diversity, honor separate traditions, and somehow hold it together," said Neil McGregor, director of the British Museum. "It is a document about regime change and a meditation on how you govern a diverse society."

Persian leader Cyrus the Great ruled over an empire that spanned from Egypt to Central Asia, including the Balkans. He died in 530 B.C. after a reign that lasted from 29 to 31 years, depending on the source.

Unlike most empires of the period, which were based around rivers, Cyrus' was a "road empire," stretching thousands of miles, said McGregor, and also the first "multilingual empire." It also had a civil service: "You can't run this kind of an empire without a great bureaucracy."

What we know of this empire came from two diverse sources: the Jewish Scriptures and the Persians' archenemies, the Greeks.

"What is striking, given the usual Greek view of Persians as barbarians ... is that, in the Greek record, one hero emerges -- Cyrus," says McGregor. "That is because both the Jewish and the Greek held him to be a hero."

So did Xenophon, Machiavelli and Thomas Jefferson, who owned two copies of the Cyropaedia, "The Education of Cyrus."

The cylinder's text shows why he was regarded so highly. Found in fragments in the ruins of a city in 1879, it proclaims that Cyrus "is going to allow the people deported by the previous kings of Babylon to go home ... They will take their gods that were confiscated, the temples that were confiscated, back to their towns and sanctuaries, and they are to rebuild the sanctuaries, and they are to pray to their gods, and, in their temples, to pray for the king [Cyrus]."

This validates what was in Hebrew Scriptures. In Ezra (1:1-4) and the Chronicles, it's said that the Jews deported from Jerusalem were "to go home, to take the temples' vessels, and to rebuild the temples." The discovery of the cylinder proved that the Scriptures were historically correct.

They also said other copies had been made, but there was no proof until, in 2009, the British Museum discovered they had parts of another copy.

McGregor says one of the cuneiform curators "read a small tablet" one day, and later that night he realized that he'd read some of the same words before -- on the Cyrus Cylinder. Excited, he called the cuneiform specialist curator to say he thought he'd found a copy.

Looking at it, the specialist said he thought he recognized the cuneiform "handwriting" of the ancient scribe. He "went off into other drawers and found another fragment of the same tablet."

The real bonus? The tablet had lines that were missing from the original cylinder.

The Cyrus Cylinder will travel from Washington to museums in Houston, New York, San Francisco and Los Angeles.

Want to go?

WHAT: "The Cyrus Cylinder and Ancient Persia: A New Beginning"

WHEN: Through April 28

WHERE: Arthur M. Sackler Gallery, 1050 Independence Ave. SW, Washington, DC 20560

CONTACT: 202-633-1000; www.asia.si.edu