I recently walked into a unmarked forsworn camp near reachwater rock ( west near sky haven temple) also a camp in eastmarch were hunters are laying in the swamp.

Do you know any other unmarked location like a cave,town,camp or something else worth visiting.

there are a few unmarked caves, can't remember where they were.
as for the camps, they're all over and pretty easy to find if you travel off-road.

West of Dawnstar, on my way to grab a scimitar thats under a boat, I was jumped by a Frost Troll who lived in a cave nearby and I was only like level 5. Pretty fun fight. Some loot in his cave too.

I also walked into a gaint mudcrab near rorikstead

There are alot of unmarked hunter and fisherman's camps in Falkreath, and one marked hunter camp. I believe it is called "Hunter's Rest," but I may be wrong.