The grid comes with the board.
184 × 184 × 88 mm assembled, on a floor 4 mm thick inside a 12 mm rim. The cell lines are scribed, not printed on, so they survive being handled.
Column C is the water.
The board arrives with its grid already in it: cell lines scribed 0.4 mm into the floor, the letters A to E sunk into one rim and the numbers 1 to 5 up the other. Four of those columns are town. The middle column has no letter on its rim, because the rim is not there. It is cut away at both ends, the C is sunk into the channel floor instead, and a ferry runs the gap.
A cell is 32 mm square, and every piece is 0.4 mm smaller than the cells it fills, on every side. That is the difference between placing a piece and wedging one. Five blocks of town take ten of the 20 land cells; the other three pieces are bridges, and a bridge is 95.2 mm long because it has to put a whole cell on each bank with the canal in between.
Which is where the board gets tight. Columns B and D are the banks every bridge stands on, and the four-cell quarter alone takes two cells out of one of them, so the clear run left for bridges is never longer than 96 mm. Three bridges end to end need 93.6. However you lay the town out, the three crossings finish shoulder to shoulder and the rest of the canal runs clear. The plan beside this is one way to do it.
Scroll to build the town and take the ferry down the canal.
184 × 184 × 88 mm assembled, on a floor 4 mm thick inside a 12 mm rim. The cell lines are scribed, not printed on, so they survive being handled.
Five blocks of town on the banks and three bridges across the water. Nothing clips and nothing glues: each piece stands in its cells with 0.4 mm to spare on each side.
Above the bridges the canal is open for its full 32 mm, which leaves 3 mm either side of the ferry's beam. Steps come down to the water on both banks.
The north bridge stands 80 mm to its parapet and carries the crossing on an arched plate 12 mm wide. Under the crown there is 44 mm of clear water. The ferry is 20 mm tall.
Three bridges shoulder to shoulder still leave 20 mm of open sky between their crossings. From above you watch the ferry go under one plate and come out beneath the next.
The last arch closes 16 mm above the water and the ferry stands 20. It is 4 mm too tall for the gate at the end of its own canal, and it stops there with its prow on the stonework.
All three bridges span the same 95.2 mm and open the same 32.4 mm where they meet the water. What differs is where the arch closes over it. Drawn to the same scale on the same water line, with the ferry, the reason it stops is not an argument. It is a measurement.
The board is the biggest thing on the plate at 184 mm square, so it is the part that sets the bed you need; every other piece fits inside its footprint. Nothing is glued, clipped or fastened, so a town that came out wrong can be lifted off a cell at a time and tried again.