The Thermae of Constantine (Baths of Constantine), the Roman bathing complex, dates from the 4th century AD. Of the once-extensive series of buildings, which resembled a palace, only the Caldarium (warm bath) and parts of the Hypocaust (underfloor heating) and the Tepidarium (warm air room) remain. The Thermae of Constantine has been listed as World Heritage Sites since 1981.
References:Stobi was an ancient town of Paeonia located near Gradsko. It is considered by many to be the most famous archaeological site in North Macedonia. Stobi was built where the Erigon (Crna River) joins the Axios (Vardar), making it strategically important as a center for both trade and warfare.
Stobi developed from a Paeonian settlement established in the Archaic period. It is believed that in 217 BCE, Philip V annexed Paionia during his campaign against the Dardani who had entered Bylazora, the largest Paeonian town.
The city was first mentioned in writing by the historian Livy, in connection with a victory of Philip V of Macedon over the Dardani in 197 BC. In 168 BC, the Romans defeated Perseus and Macedonia was divided into four nominally independent republics. In 148 BC, the four areas of Macedonia were brought together in a unified Roman province. In the reign of Augustus the city grew in size and population.