Wesley and a friend in the Denubian Alps.
The Denubian Alps were a mountain range on planet Quazulu VIII. The mountains were covered by a deep powder of snow which was ideal for skiing.
In 2364, Wesley Crusher and eleven other students were given skiing lessons by a ski instructor in a holodeck simulation of this location. In their time spent in the holodeck, the field trip was exposed to the Quazulu VIII virus. (TNG: "Angel One")