Is there a way to visualize on a Google map all places I've given a review on Google? Something similar to My Maps, but with places I reviewed automatically added.
It appears that since a few weeks it's possible.
Click on any place you've ever reviewed, then click on "Reviews", find your review and click on your profile icon. You'll be brought to a map containing your reviewed places, marked with this icon:
The map also contains all your Saved Places.
Note: this map only shows the most recently reviewed places. I don't know if it's because the Review Map is a new feature and just started tracking your reviews, or it does this by design.