Salem

Here's the screenie: http://clip2net.com/s/2uP2I
When I try placing it, it says "you can't build that there". So it means that this node is pointless, or there is a way to build it there? If not, I'm really, really sad.

Place for a mine entrance must be flat and it must be either ground (as in dirt), or paved. So flatten it first and then it will work

I get it, but that looks unfatternable.
http://clip2net.com/s/2uPh4
Here is another screenie, so you might see the height difference.
The bottom middle square says "This area is too steep to support more".
The bottom right can't be digged.

You don't have to flatten whole area. You only need 3x3 area, and it's enough that it touches the spot shown when prospecting - it doesn't have to be in the center. So just flatten few more tiles in the upper part of screenie and you should be set

Also, do you get "area is too steep" while dropping dirt or while digging? The area on bottom looks like dropping dirt shouldn't be a problem

Thank you, already tried placing not in the spot center, but im kinda new in terramorfing, so had to flatten more than 3x3 before it worked.

Yeah, dropping dirt didn't work, but whatever.