Beside the full "mountain rating", which enables a pilot to land on ANY altiport and ANY altisurface, you can get a "Qualification de site", which is a local mountain rating, valid only for one altiport, the altiport where you did your training and were checked out. Unlike the full mountain rating which is valid as long as your license is, this local rating is valid only for 6 monthes after your last landing there. After that, you need a check out to be allowed again to use the corresponding privileges and land or take off solo.
The advantage of a local rating is that it is much easier to get. Expect around 5 hours to get it. The full mountain rating requests at least 20 hours, if you have all the prerequisite : ability to do perfectly stabilized finals, with a slope exactly what it must be, and a very precise speed (+ or - 1kt). Otherwise, it will be much longer and you might even been unable to get the rating. Remember that when you land on an altiport, there is no way of going around. An "mountain" instructor advises at least 200 to 300 hours in your logbook before you try to get the full rating.
These ratings are available in two forms : wheels or snow. With the "snow" rating, you may land on snowcovered surfaces, even glaciers.