From what I've heard from a close source, Sandcastle used to be nothing more than a hotdog stand next to Lake Nokomis. It's now been transformed into a stately eatery serving the hungry park patrons. And by "mid-June" the transformation and construction should be compete, even selling beers and wines.
We had a very simple yet solid dinner. I'd recommend this as a nice change of pace to the normally busy lakefront eateries in the Twin Cities. At Sandcastle on the Monday night we went, there were no lines and little wait time for food.