Ive been to the Rainforest Cafe and eaten this behemoth of a dessert with a friend, and I too have wondered the caloric information of this item. I thought it was required for all corporations to post the nutritional information of their food items on their websites, but after an extensive internet search I have been unable to locate such information. So, I would like to provide some insight to the possible calories based on the ingredients listed in the description: "Giant rich chocolate brownie cake stacked up high, served warm with vanilla ice cream, fresh whipped cream, and topped with caramel and chocolate sauces".
Chocolate brownie (56 grams = large square): 227 calories
Vanilla Ice Cream (66 grams = 1/2 cup): 137 calories
Fresh Whipped Cream (60 grams = 1/2 cup): 207 calories
Caramel Sauce (21 grams = approx 2 tablspoon): 66 calories
Chocolate Sauce (39 grams = less than 3 tablespoons): 109 calories
Total: 746
So conservatively it is in the 750 - 800 calorie range. If you split it with a friend, be sure to cut that number in half. But for dieting purposes, I would recommend this as a rare treat after a calorie-burning day.
Hope that helps in some way!