As the Roman Empire spread across Europe ... They were also built to strict specifications, so that their ‘hypocaust heating’ would work properly. This system used water, heated in fiery ...

It was built by the Romans nearly two thousand years ago. These stacks of tiles are part of a very clever Roman invention, the hypocaust. The hypocaust was a space under the floor where the air ...

Image caption, Some Roman homes were kept warm with an underfloor heating system called a 'hypocaust'. The floor was raised up by piles of tiles or stone pillars to allow warm air to circulate.