I am assuming a "Grotto" would be something like where children go to sit on Santa's lap and take pictures with him. It may very well be called a grotto here as well, but we American's don't really call it anything .. its just where Santa is.
Originally Posted by The Mole
Kinda like a Beaver's Den is called a "Lodge" but people might not know the actual name just call it 'the place where Beavers live'
More to the point, if you said, "I sent my kids to go see Santa in the Grotto" people would probably quickly think you were talking about the Playboy mansion. The Grotto is a famous section near the Mansion's pool where -- well, things happen.
"I have always thought of Christmas time, when it has come round, as a good time; a kind, forgiving, charitable time; the only time I know of, in the long calendar of the year, when men and women seem by one consent to open their shut-up hearts freely, and to think of people below them as if they really were fellow passengers to the grave, and not another race of creatures bound on other journeys." ~Charles Dickens