First time I used Fort

[gavenkoa]

The city had one adjacent hill and AI's stack occupied it leading to a lost game.

I didn't have Iron, so my best units were Maces with upcoming Musketman against their Crossbows / Elephants / Knights.

I replayed the game from a late save building a Fort on that hill. Musketmen with their 9STR have 9*(1+.25+.50) = 15.75STR - nice against Knights 10STR (or 10*(1+.1+.1) = 12STR of their promotions).

Without Fort AI is able to concentrate horsed units as a big stack on a hill and my Musketmen cannot attack their Maces on that hill to weaken a stack.

3 waves of AI were crashed against a city and a fort, buying time to get enough Musketmen to go offensive.

Building Fort is expensive, at that stage my 6 idle Workers did it in 2T, so that cost me zero.

 

[Build2Much]

The only thing I ever used forts for (until recently) was to claim oil in the tundra/ice before I had combustion. I was missing out, they have real military use I was simply ignoring because I didn’t ever NEED to build them.

Still situational, but I will build them on unworkable tiles if they can help as a defend/attack point

 

[jorissimo]

The best use of forts is as airfields imho. You put them on unworkable tiles and each can hold 3 aircraft, like a city, so you can save hammers on airports and carriers.

 

[gavenkoa]

but I will build them on unworkable tiles if they can help as a defend/attack point

I actually destroyed tile improvement to make temporary fort.

A fort could be used by AI, if not protected, imaging how difficult would be removing of AI from a fort...

So after the use of a fort I'd eliminate any unprotected.

I was missing out, they have real military use

I've read they could host ships, and you could join two seas separated by no more than 2 land tiles with forts!

 

[Qactus]

When you have a really important resource tile improvement that is being targeted by spies (think your only aluminum while building spaceship parts), you can prebuild a fort on top of the tile improvement until one turn of completion and leave the worker in place.
Should your opponent successfully conduct their spy mission, you complete the fort within the same turn, restoring access to the precious resource immediately. Afterwards you prebuild the original tile improvement on top of the fort until one turn of completion, rinse and repeat.

 

[Major Tom]

Occasionally a canal might be handy. One tile like Panama or Suez. Obviously for people playing random maps. Works as airfield too, as Jorissimo points out.

 

[soundjata]

Occasionally a canal might be handy. One tile like Panama or Suez. Obviously for people playing random maps. Works as airfield too, as Jorissimo points out.

The quickest way to build a canal / airbase is to pluck a city (late game when you can afford it)

 

[gavenkoa]

Occasionally a canal might be handy. One tile like Panama or Suez.

Not only one tile but TWO tiles too! With 2 Forts.

The quickest way to build a canal / airbase is to pluck a city (late game when you can afford it)

See above, you could make 2 tiles canal - with adjacent 1 city + fort or with 2 forts!

A single city is limited to 1 tile length only + incur Settler & maintenance cost...