I hold the brightest of bright in a place with low light AND I am a place with low light that is not the night.
What am I?
Edit: The site wouldn't let me post the original version because it is not grammatically correct. I think it's better.
"Both brightest of bright and place with low light; what am I?"
It is one word with two meanings rather than one thing that meets both conditions.
The bright comes from above the dark goes deep underground.