Ooh, did somebody say Meracydia? I've got some facts (and speculation)!
It is mentioned in the descriptions in a few fish caught in-game. The Angelfish is a species originating from the warm coasts of the region that has recently been caught in Eorzea following the natural upheaval of the Calamity, and the Dark Bass is an invasive freshwater species brought from the rivers and lakes of Meracydia to those of Eorzea.
It is also, more interestingly, mentioned in the description of Aloe. The plant is said to be native to Meracydia- the interesting part being that the only two uses of the plant are the described utility in Miqo'te folk medicine, and its in-game use as an ingredient in a type of Miqa'bob, a traditional Seeker dish. Given that we know that the Miqo'te in Eorzea today are descended from Miqo'te hunters who came across the Fifth Umbral Era's ice bridges from a land to the south, it may not be unreasonable to posit that the original homeland of these Miqo'te was in fact Meracydia.