It is Latin. It is found in the beginning of Poe's Pit and the Pendulum, and was composed for the gates of a market he erected at the site of the Jocobin Club House in Paris.
Impia tortorum longos hic turba furores
Sanguinis innocui, non satiata, aluit.
Sospite nunc patria, franco nunc funeris antro,
Mors ubi dira fuit vita salusque patent.
--e.a.p.
Online I found this translation:"Here an unholy mob of torturers, with an unquenchable thirst for human blood, once fed their long frenzy. Our homeland is safe now, the baneful pit destroyed, and what was once a place of savage death is now a scene of life and health."
But I'd rather translate it more literally myself:
"Here the impious crowd of torturers, not satisfied by (literally of) the blood of the innocent, nourished their long fury. With the Fatherland now safe, with the deadly (this word seems to be misspelled, or else is somehting else which is missing from the dictionary) cavern now broken (also misspelled or another word), where death was harsh, life and safely now lie open."