Navigate to https://en.wikipedia.org/wiki/Chicago
Click on the "Interactive map of Chicago"
(alternatively, just go to https://en.wikipedia.org/wiki/Chicago#/map/0)
Zoom out a little

What happens?:
You see a map which is missing Lake Michigan, Lake Superior, and Lake Huron.

I first noticed this while running the bullseye.toolforge.org tool:

What should have happened instead?:

There should be more lakes.

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc: