The sink
Riddle location 2
is a reservoir...
...for all the rainwater on the island. At low tide, the water level inside the island is higher and the water can flow "out" of the island through a valve in the pumping station.
To the riddle
On the way to the Spühlkuhle you will pass the AMT PELLWORM. Count the bricks above the window.
Make a stopover at the island museum or at the spa and tourist center . Both are also a few meters away.
Now form a combination of the number of stones and the playing card with the sailing ship