While many ancient structures exist, Prague Castle in the Czech Republic and Windsor Castle in England are the most prominent contenders for the title of the oldest still standing and in use. Prague Castle, founded around 880 AD, holds the Guinness World Record as the largest ancient castle in the world and has served as the seat of Czech monarchs and presidents for over a millennium. However, Windsor Castle, built by William the Conqueror in 1070 AD, is recognized as the oldest and largest occupied castle in the world, having been a royal residence for nearly 1,000 years. Other ancient fortifications include the Alhambra in Spain, which saw its first stone fortress built in 889 AD, and the Citadel of Aleppo in Syria (though outside Europe), which has foundations dating back to 3000 BC. In Europe, these structures represent a transition from wooden motte-and-bailey designs to the enduring stone fortresses that define the medieval landscape today.