The icy caverns featured in the episode were constructed inside a warehouse which had previously been used for cold storage; and required the use of truckloads of lumber and of Styrofoam. The set would become one of the most expensive and elaborate built during the series' history. The set required a constant temperature of in order to maintain the real snow and ice used to decorate it. This refrigeration allowed the actors' breath to visibly fog up, and allowed the cast to "have a place that feels real" to aid their acting.