It is Aeonium, I believe 'Suburst', and it is crested. I wish I had one :)

What a very interesting plant! Any idea how old it is? Looks ancient!

The Sunburst looks right. Thanks! "Crested" is new to me. I don't see any pics this big.

This plant is over 10 years old. Beyond that I don't remember. I had another 1/2 this size that the gardener recently threw out!

In right conditions, they grow quite large. I would think that in ground, as yours, even bigger. In pots, the size would be more limited. Too bad other one was thrown away! These are desirable by some ppl - I don't think I saw crested aeonium for sale around my area (but I do not 'stalk' stores :) - only some other succulents.

According to what I read, it is flat, like yours, if cresting starts early.

This will explain better than I can - many articles about this mutation are available, here is just one of them.

Cool link Rina, thanks for sharing it.