70

According to the Sixth Doctor, 70 was the year the Romans began construction of the Colosseum. (MA: State of Change)

In the early 21st century, archaeologists found a Roman mosaic which they dated to this year. On the mosaic were scenes, grapes - and a Dalek. This suggested there were Daleks on Earth in the 1st century AD. (QR: I am a Dalek)