Underfloor Heating (UFH) was popularised by the Romans, however the earliest example of UFH found dates to 550BC and the Temple of Artemis at Ephesus.
Celebrated as one of the Seven Wonders of the World, this Greek temple was rebuilt from ruin by the architect Chersiphron of Knossos, who added hypocausts to create the world’s first known example of central heating. So yes, UFH is officially the daddy of all central heating and is, at least in part, one of the Seven Wonders of the World.
Hypocausts, the world’s first central heating system
In the absence of electricity, ETFE insulation and polyethylene pipes, servants would maintain a fire that would vent through the void beneath suspended stone floors and up though ducting within walls to provide all round warmth throughout, with a system capable of using the heat from a single small fire far more efficiently than alternatives at the time could, just as modern UFH systems do today.