Hi, it looks like something you might have downloaded. Probably not something you have created yourself, since you would remember that. Try unchecking everything in the Places panel on the left and see if it goes away. If you can find it you can delete it.
If that doesn't help try unchecking everything in the Layers panel too, though I tend to think it's more likely to be in Places.
If you don't see the Places and Layers panels, you'll need to check the Sidebar option in the View menu.