In reality, there is no point during which one can claim "It all began..." because history begins with the planet's creation. We'll jump foward to the KNOWN history of Barcelona...
Barcelona's first settlements are known to have existed in the Neolithic period, also know as the "New Stone Age" (the last part of the Stone Age) from 5,500 to 2,500 B.C.. And at that time, Barcelona was NOT known yet as "Barcelona" - not for another few thousand years more.
Sometime around 230 BC the northeastern corner of the Iberian Pensinula was occupied the Carthaginians. One Carthaginian, Amilcar Barca, is given credit for the actual founding of what was then called "Barcino". This began a particularly bloody period of Barcelona's history. Next, "Barcino" was invaded by the Visigoths and later the Muslims. Armies from what is now France battled back the Muslins in 801 AD. It was at this time at which "Barinco's" plains and mountains where the original "Catalans" can be traced. Linguists assert that these "Catalans" spoke a similar language which still exists today in southern France, called "langue d'oc".
By the end of the 1st century BC the Romans establish a colony and the city proper of Barcino was founded with population of 1,000. Some of their strategically defensive walls still exist in the Gothic Quarter and roman ruins are un-earthed nearly everytime a new below-ground parking garage is installed, new metro lines are dug-out, or when other excavations take place in the old parts of the city.
Around the same time the Romans colonized "Barcino", at the 1st century BC, they were also busy conquering the rest of the Iberian Peninsula. Around 400 AD the Visigoths invaded the Peninsula, pushing out the Romans, and changing the name of "Barcino" to "Barcinona" - sounds familiar, doesn't it? After the Visigoths, "Barcinona" was invaded and conquered by North African Muslims in the 8th century while in the late 9th century Barcelona was ruled by Count Wilfred the Hairy. It was Count Wilfred the Hairy who unifies the county of Barcelona with other Carolingian territories and establishes hereditary succession.
During the years 1000 to 1200 Barcelona becomes one of the most powerful and influential trade cities on the Mediterranean Sea. During this time the city is growing and people are migrating to Barcelona for work.
During the medieval times, Barcelona establishes itself as the political and economic center of the Western Mediterranean as well as one of the main residences of the court of the Crown of Aragon.
It was during the 13th to the 15th centuries that a building boom took place, a time when many of the beautiful Gothic Quarter buildings were constructed, a time at which Barcelona was at its peak in power, influence, and richness. And as is so often the case, all good things must come to an end. By the 15th century, "The Plague", which was ravishing much of Europe, so did to Barcelona, banks crashed, and Barcelona's power and influence came to a near-end.
With the discovery of the Americas in 1492, King Ferdinand & Queen Isabella gave less attention to Barcelona and the Mediterranean and focused efforts and economic support to their interests in "The New World. The riches gained by the crown from the Americans did not benefit Barcelona, however, and the seat of the Monarchy was moved from Barcelona to Madrid in 1561 by King Philip II who was born there, the capital of the new Spanish Empire - although some historians argue this year.
Things were about to get worse for Barcelona and Catalonia. During a struggle for succession to the Spanish throne in 1702, Catalonia supported the Archduke of Austria while the rest of Spain supported Felipe of Anjou, a Frenchman. In 1714 when Felipe of Anjou won, Barcelona and all of Catalonia was suppressed politically & culturally.
Finally, after 1778, the Crown allowed trade relations between Catalonia and the Americas, slowly improving Catalonia's economic standing and giving Barcelona a taste of the power they once held. The mid 19th century brought about Spain's first industrial revolution, led by Catalonia, which was largely based on cotton (launched from Barcelona) wine, cork, and iron industries as well as the textile-manufacturing sector.
More Barcelona history soon...