Yes it is real. Yes it is chalk. Yes you could walk right across that.

Check it

 

That's insane!
I wish I had some crazy skill like that guy does. That's awesome.

 

i saw that in a magazine, i think it was maxim. supposedly he makes his own chalk that wont weather as quickly, but that is definately a talent.

 

All I can say is WOW! But I would like to see it at a different angle. The angle its photographed at is the POV the artist had in mind. You can tell by the lip of the "pit" that you can't see down that sides wall.

 

Amazing

If you click the other pages on the bottom you can see more examples:

http://www.kurtwenner.com/street/street02.htm