The Piazza della Repubblica is undergoing some renovation right now. Are these Roman ruins visible? Don’t know, but I can only imagine. This was the center of the Roman army camp that began the city many moons ago.
You can read more about it here: http://firenze.repubblica.it/cronaca/2018/03/29/foto/la_firenze_antica_riaffiora_sotto_piazza_della_repubblica-192510635/#1