Castrum Centri is Castrum Novum

[Chewy2nd]

Alphinaud says when you first arrive in the Toll (when spoken to)
"In the wake of the Calamity, the XIVth Imperial Leigon occupied what remained of Castrum Novum eventually rebuilding it and naming it Castrum Centri"

Just for those who suspected Novum might be in Southern Mor Dhona.

[Rocl]

The sightseeing log makes it clear as well in entry 077 - Castrum Centri

"Castrum Centri was erected with material salvaged from the ruins of Castrum Novum--the Garlean Empire's first major outpost in Eorzea, constructed in the final year of the Sixth Astral Era by the VIIth Legion legatus Nael van Darnus. It houses several ceruleum mining pits, a magitek manufactory, and the Phantom Train, used to transport ordinance to outlying castri."

[Chewy2nd]

Aye, I'd always thought as much, they wouldn't have built a whole new fortress from the ground up, they'd have just salvaged what was left of Novum to rebuild. Make's it less obvious that they were setting up such a large facility too (not that Revenant's Toll would have been paying attention, since it was just farm land back then, plus the old Camp was in ruins).