I think its traveling merchants
<em>Dura-Europos</em> was an ancient city located in the vicinity of village of <em>Salhiyé</em>, Syria, along the Euphrates river, close to the Iraq border.
Christian places needed to be discreet or secret around 240 A.D.; thus earlier congregations worshiped in private houses of wealthy members; some of those houses were converted into churches, and the house in <em>Dura-Europos</em> was one of those conversions.
So the purpose of the frescoes was to celebrate Christian worship secretly, and to illustrate the old testament writings, mostly for the illiterate people who couldn't read the sacred books, as a medium of what they called "<em>hope of new spiritual birth</em>".
They all help us in the United States to be what it is today
The answer is "their religion"
