Probably the most publicized peaceful era is the Pax Romana. Latin for "Roman peace," this period of roughly 200 years was made famous by the 18th-century historian Edward Gibbon in his landmark book "The History of the Decline and Fall of the Roman Empire" [source: Encyclopædia Britannica Online].
Gibbon set the beginning of this time at 27 B.C., during the reign of Gaius Julius Caesar Augustus (otherwise known as Octavian, great-nephew and heir of Julius Caesar). Augustus set in motion a new brand of foreign policy for Rome, which had previously been focused on expanding the empire as much as possible. Instead of pushing an agenda of expansionism, Augustus advocated a shift toward prosperity and pacification within the borders of the empire. Civil rebellion fell dramatically during this time (though it didn't stop entirely). Ceremonies such as closing the Gates of Janus, which signaled the achievement of world peace, as well as the construction of the Ara Pacis ("Altar of Peace"), demonstrate the growing importance of a peaceful existence in the Roman Empire. Historians usually pinpoint the end of the Pax Romana in the year 180, when emperor Marcus Aurelius died and passed the throne to his son Commodus. Commodus didn't share all of his father's ideals and military philosophies, and thus the emphasis on peace went by the wayside.
But even though Augstus' overall intention seems to have been to maintain peace in the empire, there was still violence during the Pax Romana. Rebellions in Hispania (modern-day Spain and Portugal) didn't stop until roughly 19 B.C., and the border between Rome and Germania was hotly contested during much of the Pax. During this period, Rome invaded and annexed Britain -- not the most peaceful venture, particularly from Britain's point of view. So, even though the Roman Empire gets good press for the Pax Romana, it wasn't the most peaceful time in history.
For our next contender, let's head over to the steppes of Eurasia. Was peace another commodity on the Silk Road?