"The inside of the cave is dark" is the natural sounding sentence. "place inside" does not add any meaningful information. That form would make sense if you wrote "The rocks inside of the cave are sharp" or "The air inside the cave is musty" Cheers from Canada
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
lucas21c1. The inside of the cave is dark.2. The place inside the cave is dark.When referring to the geometric position of a part with respect to the whole, you don't normally add "place", "location", "area", or any other such synonym.