My current saga has a trader magi who is interested in creating an underground canal going all the way from Lubeck in the north of Germany to Geno on the Mediterranean coast.
Obviously such a canal, under that Magus' control would be insanely profitable for shifting goods, perhaps even more so if he allowed others to use it and charged tolls.
But how to achieve such a massive engineering work?
Lubeck to Genoa is about 1,060,000 paces (1060km). So thats our distance sorted. We'd want a tunnel wide enough to have two seperate canals, allowing travel in each direction, so maybe 5 paces wide for each canal, plus a pace wide raised wall between them and paths on either side of two paces width, so that's 15 paces across. Height, you'd want it to be about 4 paces high from the water level, maybe two paces deep, so 6 paces high. This means that each pace in length of the tunnel is 90 cubic paces of space. This will be important later.
How to make such a tunnel? With Perdo terram, you can destroy a cubic pace of dirt at touch range at level 10 (base 3, +1 to affect stone, +1 touch, +1 part). Add two size magnitudes to put it up to 100 cubic paces of stone and you can bore one pace of the tunnel with a level 20 spell. This would require 1.06million castings to complete. It would also create a tunnel that isn't necessarily stable. We'd need further spells to create pillars in the central wall dividing the canals to hold the roof up, and maybe additional supports. If we bumped the level of the spell up to 40, by adding another 4 magnitudes of size, we could bore a tunnel 10,000 paces long. Much better. This would only require 106 castings. Which is a lot, don't get me wrong, but not crazy for something this epic. Knock it up to 50, make it a ritual by adding two more size reqs and you've got a tunnel bored in a single spell 1,000,000 paces long (close enough to get close to genoa if you make sure you have a really straight direction, lets not quibble about a mere 60km.
All this assumes that we are digging through bedrock of course.
It also leaves the following problems to resolve
- Air. You need some or all the people working the canal boats will be dead by the time they reach genoa/Lubeck
- Water. Boats tend to work best on water, you'll need lots.
- Way stations. Even with a magically powered canal boat, 1000km is a long journey, you'll need spaces to park the boats up, rest the crew, sleep, etc.
- Lighting. People work better in the light and don't get as terrified
- Security. Earth dwelling faeries, jealous local rulers, rival magi. A project this epic will need protection and alliances.
- Access. If something happens in the canal, you need to be able to access it close to where the trouble is rather than potentially travelling 500km from one of the entrances.
- Arrangements with fellow merchants. A tunnel like this is going to be fantastically profitable. Other merchants will absolutely want in on it. It would be very hard to keep it quiet and also shift large amounts of goods. Maybe best to get other merchants onboard by allowing them either access with a fee, or maybe even start a joint company with some other powerful merchants, a trading coster specifically to handle the cross continental trade, create a monopoly and trust in the wealth and power of your coster-allies backed by your own magic to see off any potential rivals.
So, what other ways could this canal tunnel be fashioned? And how could we get around some of the problems? And are there any other problems I've missed?