Help with building question plz

[Olaf Blackeyes]

Can someone tell me WTF this is and why it costs half of Europa AND takes 1000 years to build?

[a completely inoffensive name]

Umm, it only takes 15 years to build...

[Lysimachos]

Basically it gives you a huge trade bonus. I prefer waiting with construction of one of these until I feel safe that I won't need to build something else there in a while

What it is? Well, the provinces have natural harbors of different sizes. Some provinces provide a natural harbor that is large enough to house a Large Trading Port (for example Carthage). In provinces which have a natural harbor that is not as big, you can build that "Extensive Large Trading Port Upgrade" to bring your trading port to the highest level.
If the natural harbor isn't even sufficient to build the second highest level, you can build a "Extensive Small Trading Port Upgrade" to bring your trading port to at least the second highest level.

These upgrades are extensive (and thus expensive) because you have to change the coastline, excavate port basins, build artificial wave-breakers and so on. I hope you get the idea

Edit: By the way, it's not really that expensive, you have to remind yourself that you won't build anything else for 15 years, and a cost of about 1067 per turn is not that bad really.

[A Very Super Market]

But you have to pay of front, so it is costly in that you won't be building or recruiting for 10 turns to save up for the damn thing. Maritime trade is nice and all, but this is too much.

[Ardri]

A trading port of this size probably wouldn't be built until there was a substantial economy already formed and that is the same approach that it requires in the game. If you have a decent size economy (10-15 developed cities) saving enough to build the trade port shouldn't be too big of a deal. Just need a nice stretch where you are not at war so you aren't cranking funds into your military.

[HunGeneral]

Is the bonus this Port gives really woth the price? I mean to my judgemant mines are already expensive and need long to be built but give lots of cash. However I wouldn't start building something like that port without having atleast half of the whole mediteranian see (or, + the black sea, and lots of Indian cost would also be nice)