Colchester, known as Camulodunum in Roman times, was a large town in the English county of Essex. It constantly rained there, even stretching back to the 1st century AD. Once, Ian Chesterton spent "one of the worst weekends of [his] life" there with a girl; it rained without end. (PROSE: Byzantium!)
Camulodunum was the Roman capital of Great Britain during the Roman occupation, which lasted from 43 to the early 5th century. It had previously been the Trinovantes' capital. (AUDIO: The Wrath of the Iceni)
The Eleventh Doctor once spent a short amount of time there, living with Craig Owens. During this time, a spaceship hidden by a perception filter abducted and killed a total of seventeen people looking for a compatible pilot. Together with Craig's friend Sophie, the Doctor and Craig stopped the ship. (TV: The Lodger)
When returning to Colchester to say good-bye to Craig before his impending death, the Eleventh Doctor discovered that a Cybermat was interfering with the electricity grid and several people had disappeared. He then got a job in the toy section of the department store Sanderson & Grainger and discovered the crashed Cybership. It was later destroyed by an emotional feedback caused by Craig hearing his baby son cry during Craig's Cyber-conversion. (TV: Closing Time)
Brandon's Information Solutions had an office and call centre in Colchester, which once employed Craig and Sophie.