An archaeologist is like a detective, looking for evidence (clues) about how people used to live long ago.
Sometimes the clues are found by accident. A digger moving earth in a peat bog in Cheshire found a human body buried deep in a bog. The shocked workmen called the police - they thought the man had been murdered.
The man had been knocked on the head, strangled and his neck had been cut. Imagine their surprise when archaeologists worked out that he was an Iron Age Celt who had been killed 2000 years ago!
Only the upper half of the man's body remained. Archaeologists found food still in his stomach after 2,000 years! His last meal was bread. Here was a fantastic clue to the world of the Celts, pickled in the bog.
The bog man was naked when his body was found. Unfortunately, evidence like clothes, shoes and pots are rarely found because they rot in the soil. But things made of stone and metal do not rot and these are the clues which tell us about the Celts - but give us only part of the story.
The early Celts didn't leave books behind because they didn't read and write - word of mouth and memory were the Celts' way of recording events.
But luckily, the Greeks and Romans did write about the Iron Age Celts. They tell us that the Celts lived in tribes, they wore gold and loved to fight and drink wine. They also wrote about the power of the Celts' priests, who were called druids.
The druids knew how to keep their gods happy - they sacrificed food, precious objects, and even people to their gods and goddesses. The Snowdon bowl in the picture was probably a gift to a god or goddess, as it was a valuable, important treasure. The design on the handle of the bronze bowl looks like an animal's head. Two biology students found the bowl's remains in 1974 on the north-east side of Snowdon, north Wales.
Archaeologists think the bog body from Cheshire was also a sacrifice to the gods. We can never be absolutely sure what happened in the past though. We can only piece together the clues and, with imagination, work out what happened.