What should I expect from a Belgian double (dubbel)? I know dubbels are considered as strong beers, but what should I expect in when I try one of them?

What are their defining characteristic? What should I expect in term of taste, foam, color and mouthfeel?
As with any style, there's a fair deal of variation from one brewery to another.  At a high level, though, you can expect them to be darker (although not stout-dark), rich, and malty.  Expect a complex taste, with many notes and flavors.

More specifically, the BJCP have this to say (abridged):


Aroma: malty sweetness, hints of caramel or chocolate, and moderate fruity esters.  Some will have a little spice to them.
Appearance:  Dark amber to copper in color, Large, dense head.
Taste: Same as aroma. Alcohol flavor, if any, should be mild and not solvent-y.  No or minimal hop flavor.
Mouthfeel: Medium-full body. Medium-high carbonation.


See here for the full description.