Schönbrunn Palace with its associated park belongs to the UNESCO World Heritage since 1996. The first construction from 1638 was destroyed during the second Siege of Vienna. Four years later Emperor Leopold I. commissioned the famous architect Johannes B. Fischer from Erlach for a representative new construction. The first plan designated a construction which should have surpassed the Palace of Versailles. Due to financial reasons this could not be realised and a smaller alternative was built, between 1696 and 1701. The contemporary architecture today originates from 1743 under Empress Maria Theresia. The palace grounds houses the oldest still existing zoo in the world, which was established in 1752.