Silvia, I have been comparing your with the one I made in ARC/INFO.
![](twodems.gif)
On the left is my DEM clipped to your mask.
We can see here that your DEM has many bad artifacts in the flat areas.
![](elevations.gif)
Looking at a small area in the mountains, ARC/INFO looks fairly good
and your DEM looks very bad.
![](slopes.gif)
The slope maps show problems with your DEM.