instafluff, this is a fantastic work!
WOW! This is crazy! Extraordinary! I never imagined that something like this could be done in C3C! ...and they are also all customizable... WOW!
Thanks, I've been working on this for quite a while. Just didn't want to reveal anything until I was sure it would work. Getting unit movement over it was not too hard, but the visual placement algorithm is very complex, with many PCXs overlayed on top of each other to get the effect. But it finally works.
Is this cosmetic or does it function so that the bridges allow land units to cross coastal tiles and the canals allow sea units to cross land tiles? If so that's a complete game changer. How does this actually work? I can only assume it's magic.
It's the real deal, not cosmetic

. The AI already can use both, as I wired it into the core game movement code (only if enabled, of course). The Ancient Cavalry you see on the bridge is an AI player.
Bridges and canals are both districts, so building them is essentially the same as workers building any other district. To have workers be able to build bridges though, you'll need to have
workers_can_enter_coast = true in the C3X config (that's true for maritime Wonders and Port districts too). Once built, bridges & canals are automatically factored in when Civ 3 determines fastest paths between 2 tiles. It goes without saying that Flintlock's work on C3X really makes all of this possible; I just had to make the art and think through the mechanics.
Let us hope, that the AI will use these canals and bridges also somewhat properly. Wadi Rum is also nice.

And with some small changes in the graphics, the canals will allow navigable rivers at least for preset scenarios.
Absolutely (and thanks, regarding Wadi Rum, desert Natural Wonders are tricky!). I have ideas around how to make sure the AI sensibly build canals and bridges, but more to come on that. For now at least the AI automatically uses them, if getting from A -> B is faster on that path.
And right, you can certainly change the graphics to make them look like rivers, then pre-place them. The screenshot I showed is all canals I pre-placed using the editor, as I was testing the UI.
- will the bridge be able to be built over the canal?
No, they are both districts under the hood, so a tile can only have one at a time.
- I don't know what it will be like if the ships stop under the bridge.... maybe there should be a setting that "skips" the bridge tiles and stops on the next tile... ?
Movement-wise that would get very complex. For now, both land and sea units can go on both bridge and canal tiles.
- can a movement penalty be introduced when units (or only some units) cross the bridge?
Possibly in the future. I can see how this would make sense and be useful. I need a lot more time to test and make sure the AI uses these sensibly first though, so one thing at a time
- can the bridge be "blown up", or can elements of the bridge be "blown up"?
Yes, bridges are just districts, so can be blown up like any other district. Interestingly if a land unit does so (pillaging, not bombing), it's basically suicidal, so we need to think through whether that's a bug or a feature.
Maybe a new unit will appear... the sappers(military explosives specialist) - which will mine the bridge and the bridge will explode randomly on 1, or 2, or 3 turns!!
Very cool idea. I think the forthcoming Lua implementation would make that kind of thing much easier.
- maybe a floating bridge could be built, like the army does?
Sure, this would enable that kind of modification.
The canal is a dream come true, from now on a "Panama Canal" can be built to shorten the shipping route!
That was my long held hope & goal too
- can it be avoided somehow, building around.... cities, or a territory?
Can you explain more on this? Avoided in the sense of AI/human not building it somewhere?
Somehow to have a "pre-route" between two "waters"? Anyway, once built, it also becomes a defensive element!
- from the navigable canal, will it be possible to connect the irrigation, in the classic way or through a "thinner" canal?
Yes, you can add defensive values to it and pre-place canals. Regarding connection to irrigation, possibly, but that would need to be in the future. Logically though that makes sense to me.
Maybe... in relation to irrigation... a "thinner" canal could be built, connected to a water source, lake or river, to bring water to an area, and if an element is interrupted and water no longer comes to the fields... the canal would look empty and the lands would no longer have irrigation... until the irrigation canal is repaired!
That's a cool idea but would take some work to implement! Probably not in this next release.
Maybe in the modern era, drilling in the ground should appear, to have drinking water and water for irrigation... It's an idea!
Sure, that'd be cool.
- can the channel be blown up, bombed, damaged?
Yup, same rules as all other districts. Like bridges with land units though, if an AI ship
in the canal destroys it by pillaging, the unit destroys itself, so I need everyone's help in thinking about whether to prevent the AI from doing this, or what to do.
Natural Wonders look really good, from my point of view!
Thanks!
... that building under construction is... the Bach Cathedral?
...so more Building Wonders are appearing? If so, Super cool!
Yes, a few more Wonders will be coming in the next release.