From the brewery:

Rochefort 10 is dark brown in colour with a creamy beige head. It is best served between 12 and 14°C, releasing an explosion of intense, complex flavours on the palate, with notes of coffee, chocolate and spices.

The number 10 does not refer to the alcohol content; it comes from an old Belgian unit of measurement that expressed the density of the wort.

A beer unanimously recognised as one of the best in the world.