Question: [![enter image description here](https://i.stack.imgur.com/vXXGd.png)](https://i.stack.imgur.com/vXXGd.png)

How can I smooth all crown but don't smooth the top of the crown? I did a subdivision surface, but this didn't work. All crown became smooth and changed form.

Answer: 
Just above the Mean Crease setting that kei suggested is the Mean Bevel Weight (for edges, not the one for vertices). My usual method is to set the edges Mean Bevel Weight to 1.0, then add a Bevel modifier, making sure it's above the Subdivision Surface modifier in the modifier stack, and in the Bevel modifier making sure the Weight button is selected, not None. Adjust the Bevel modifier's other settings, Width and Segments, to taste; Segments is usually 3 for me.

This allows you to control the rounding / beveling of those specific edges separately from whatever the Subdivision Surface modifier does.

Alternatively, instead of using Mean Bevel Weight you could use a vertex group.

Sometimes you simply want the "obvious" edges not subdivided by the Subdivision Surface modifier, for example with a cylinder I want the top and bottom edges left alone. In that case I can select the Bevel modifier's Angle button, changing the Angle value to 80 or whatever if necessary. Using this method, if you add a cylinder and set the number of vertices (sides) to 6, it will still turn into a cylinder when you add the Subdivision Surface and you have the Levels high enough (3 or more).
Add in more loop cuts on the subsurf mod. That should do it. I take it that smooth shading doesn't work?