These blueprints show the expansive mountainside which will be built along the backside of the facade, framing the castle and adjacent village. Frozen Land (as it is currently known) is set to receive a replica of the Frozen Ever After attraction currently in the Norway Pavilion at EPCOT.
Source: https://wdwnt.com/2020/02/layout-revealed-for-upcoming-frozen-themed-land-expansion-at-disneyland-paris/