Sil'dih is underground at this point according to lore. It was destroyed in one of the Umbral Eras and eventually buried by sandstorms. It's most likely near-by Copperbell Mines because there is a section of the mines called the Sil'dih Aquaducts. You can see it on the map and it was used as the area you fight the Lambs of Dalamud in that one live event quest.

That's all I know about it. I'd love being able to time-travel back to explore the city (like in that one XI expansion where you time-travel).