Well, National Projects are built in cities, not out on the map itself. Determining where to place those canals might be a bit problematic, yes?
Originally Posted by BammBamm
So, here's my counter-idea:
• Instead of building a Wonder or a Project, you build a unit: "Canal Excavator".
• You build this (expensive!) unit wherever you like, then move it to a hex where you want a Canal to be placed. Order the Excavator to, er, excavate ... and after several turns, the unit is consumed, and voila ... Canal!
• Now, adjacent Canals would link up to each other in the same way adjacent Roads do;
• Canals come with a free Road improvement, in the same Hex. This can be upgraded to a Railroad, without damage to the Canal. (This way, Roads or Rails that you want to "cross" the canal with, can and will do so. When this happens, bridges should be displayed where needed/appropriate, of course.)
• Naval Units can move into any hex that has a Canal (a line of Canal hexes crossing a stretch of land, would thus allow you to move those Naval units across that landmass). Embarked units disembark, and use the (provided) Railroad;
• Any City adjacent to a Canal, gets it's own Canal for free, of course (just like Roads and Rails);
• Even better: any City which has a Canal adjacent to it, can also build Port/Harbor buildings, as if it were adjacent to a Lake or Coast hex;
• Canals cost twice as much to maintain as Railroads. This cost can be reduced by Social Policies, just as with Roads/Rails;
• Finally, Canals "conduct" Fresh Water - their hex, and the hexes adjacent, are considered to have Fresh Water access. (Reason enough itself, to build a network of canals in a Desert ...!)
EDIT TO ADD: Canals should only be constructable adjacent to River, Lake, Coast, or other Canal hexes.
Now, there's still room for the Wonder - whichever large Canal you care to name it after. What might it do?
• Upon completing the Wonder, get X number of free Canal Excavators (say, 5 or 7), which appear outside the city where the Wonder was built;
• Future Canal Excavators cost 20% or 25% less to build, and excavate canals 20% or 25% faster (in 3 turns, instead of the 4 or 5 normally needed);
• All canals produce +1 gold when worked by a Citizen.