Duplo baseplate with a river
A duplo-compatible base plate with a river in the middle. You can easily print a two-color version of it by swapping filaments after printing the river level.
There are two versions, with and without a little island on the river, I only tested the version without the island though.
The dimensions of the studs were calibrated for printing on a Prusa MK3 with PLA, and may not be accurate on other printers or with other materials.
A Hilbert curve on the top layer makes for a nice finish.