1. Four millennia ago, the mix between one of the first waves of Indo-Europeans and pre-Indo-Europeans populations gave rise to the Celts, in the (nowadays) southern Germany, between the river Rhine and Danube. The Celts developed a skilled iron metallurgy and this allowed them to produce powerful weaponry. During the La Tene epoch, between the 5th and 1st centuries BC, the Celts were involved into an expansion movement. They occupied most of present-days France and, through the Pyrenees Mountains, they entered the Iberian Peninsula, colonizing its west and north and creating powerful walled settlements. In southern France, they even attacked the Greek colonies, like Massalia (today Marseilles). During the 8th century BC, the Goidelic Celts entered Britain (inhabited, by those times, by pre-Indo-Europeans). During the 3rd-2nd centuries BC, the Briton and Belgae (from modern Belgium) Celts entered Britain. The Britons forced the Goidelic Celts to leave for Ireland. The British pre-Celt populations used to bury their dead in large stone tombs called dolmens and practiced a cult of the Sun, involving huge monoliths (like in the case of Stonehenge) in their rites. Thus, Stonehenge was not built by Celts!
The Celts descended along the Danube and entered Northern Greece and Thrace, having bloody conflicts with the Dacian tribes around the Carpathian Mountains. During the 3rd century BC, the Celts entered Asia Minor (today Turkey). But beginning with the 2nd century BC, the Celts in Central Europe were removed by the Germanic tribes.
2. Initially, the Celts were an agricultural people, inhabiting palisade villages (defending against both enemies and beasts). Celt houses were trunk-made huts. The Celts usually deforested an area, raising settlements inside the forests. Plows were driven by oxen or horses and later they were wheeled. The Celtic populations also kept sheep, cattle and horses. The Celts practiced, at the beginning, pottery without knowing the potter's wheel. At the contact with Mediterranean people, they started using it. The Celts hunted using dogs. Gold and silver collars, earrings, diadems and bracelets were imported from the Mediterranean area or made by Celt craftsmen. Amber from the Baltic regions was used in jewelry. Men used to wear a torc, a gold or silver made rigid collar with two bumps on the extremities. The Celts made from iron, besides weapons, harness pieces, plows, chariot pieces, and many other tools.
3. The Celts were very religious people, practicing a cult of the nature's powers, which the fertility of the land and harvest depended on, thus prosperity or hunger. The political division of the Celts and the fact that each tribe worshiped an own god led to the existence of over 400 Celt deities, each one found in a specific area. Many had an abstract character, being representations of love, war, sun heat, death and so on. Their images, carved by artists, often had a human body and animal head (deer or ram). Cult rites were celebrated in the open, in places where large trees, worth to be considered sacred, grew. On the branches of those trees, the Celts hung amulets and exvotos destined to win the god's favors and chase away the evil spirits. Many of these ceremonies were accompanied by bugle sounds and the invocation was made by a druid (priest). In Britain, druids used to gather at Stonehenge to make sacrifices and offerings (even if the monoliths had a pre-Celt origin).
4. There is an image of the blond, blue-eyed Celts. In reality, the Celts were a mix of blond, blue-eyed Indo-Europeans and dark-haired pre-Indo-Europeans; thus, even if many were blond, not the majority of the Celts were (like in the case of the Germanic tribes). Today, only 5 Celtic languages survive: Breton in the French Bretagne (this is not a survivor of the Celtic Gaul language spoken before the Roman occupation of Gauls, but it descends from the language spoken by Briton Celt refugees during the Anglo-Saxon invasion of Britain), Cornish (in Cornwall, southwestern England), Welsh (in Wales), Scottish Gaelic (in northwestern Scotland; this language was brought from Ireland, not being closely related to Welsh), Irish Gaelic (in Ireland).
5. Celt warriors used rectangular shields and straight swords. It was THE CELTS, NOT THE VIKINGS, WHO WORE HORNED HELMETS. Sometimes, warriors were buried together with their chariots and horses.