(Spain) Primarily a method employed in the production of Sherry, the solera system may also be found in use in Languedoc-Roussillon and anywhere else involved in the production of fortified wines such as Madeira, Marsala and Rutherglen (Australia). Barrels of wine are arranged in a vertical system, at least three barrels high. The lowest barrels contain the oldest wine. As this is drawn off for bottling and sale, each barrel is topped up with younger wine from the barrel above. In the uppermost barrel the latest vintage enters the system, keeping it fully topped up.