For example they all lived in round houses made out of straw. Most of the cooking was done in the house. These round houses are found in villages all over Europe.
In the Celt villages, there were druids. The druids were holy men who were believed to have to have special abilities like being able to turn things into things! The Celt religion is called Druidism. Druidism says that there are spirits that live in lakes and trees. The Celts were also very superstitious, they believed that the number 9 was magic, and the number 3 was evil.
The Celt tribes shared similar beliefs because story teller’s called bards traveled between them sharing epic stories like the one called Beowulf. Bards had grueling training. For example, they had to lie down with a rock on their stomach and a sack on their head. They also had to recite stories from memory 100 times until they fainted, they memorize it, or they got dragged off to be sacrificed by the Druids. These bards traveled all over Europe sharing stories.
So the Celts were pretty connected for being so spread out!
The Cut-throat Celts (Horrible Histories) (9780590139724): Terry Deary, Martin Brown: Books