This is a Duplo-compatible baseplate with a river in the middle.

Major thanks goes to pwl_b, who created the original model of this baseplate. See remix link for details, credits and original model.

Improvements and changes to the original model:

1. Enlargement of the base plate to 15x14 knobs (240x224mm) to fully utilize build plate size of A1/P1S/X1C.
2. Calibration of the knob diameter to 9.65mm for a perfect and snug fit - optimized for printing with P1S and PETG. Print profiles attached accordingly.
3. Adjusted the path of the river so that it starts/ends in the middle of base plate and moreover, runs perpendicular to the end of the plate. This should allow you to print multiple of these plates and attach them to each other - but I haven't tested yet.
4. The height of the base plate has been reduced to 19.2 mm in total (which is the same height as a regular Duplo brick and allows for easy extension of plate)

P.S. The dimensions of the knobs were calibrated for printing on a Bambu P1S with PETG. It is might not accurate on other printers or with other filaments. I recommend to test with a small print first, esp. because fit can vary with each type of filament.

Please let me know if you have additional requests for enhancement, ideas, or question.

Update: I added more versions of this base plate

1. 90° curved river (left and right curve) → https://makerworld.com/en/models/527918  
2. Vulcano Island → https://makerworld.com/en/models/799632