Quote Originally Posted by Future Esthar
Hey,I am thinking,how did the Estharians cross the Salt Lake?
It was a Lake back there.
Boats and bridges are quite plausible explanations. Both of those things could have deteriorated over time, thus explaining why no sign remains of them. Salt lakes have very high bouyancy, so large floating platforms could also have been used. They may also have gone over the mountains surrounding the lake.
And how was the horizon bridge built?
The bridge have great columns that sits on the Sea floor and extends very far.
Here is the answer:
FH is not only a city but a ship working with different forms of energy.
The three mettalic floors enables them to build the bridge and to clean it.
It could even be that it has subaquatic floors or the factories along with the mayors house served to cover people underwater (supposing it works as a submarine).
...What would be the point, though? There are factories in FH; they're plainly visible on the surface. The Horizon Bridge connects the eastern and western continents, that's all. The town of FH was founded by Esthar scientists who were ousted by Adel. FH allows them to live in peaceful seclusion, while preserving their technology and pacifist ideals.

As for the construction of Horizon Bridge... the Deep Sea Research Centre proves that (in FFVIII's world) it's fairly simple to build a column that extends right down to the sea floor.

Nothing in the game ever suggests that FH is mobile, though.