There is a hole in my floor

But it is not what you think.

This is a real hole, with a specific purpose. Photo by author.

Every time I walk the corridor alongside the den in my house, out of the corner of my eye, I see this dark black hole in the floor. A hole in the floor? I need to get that fixed. I stop, turn to look. I need to assess the damage. Is it really a hole? Is it something that got spilled on the floor that needs to get cleaned up?