After the restoration of Louis XVIII. as a constitutional king, the treaty of Paris between France and the allied powers was signed on May 30, 1814. The treaty amounted to a settlement in outline of those territorial questions in Europe in which France was concerned, and aimed mainly at the construction of a strong barrier to resist further encroachments by France on her neighbours. The French boundaries were to coincide generally with the limits of French territory on January 1, 1792, but with certain additions. The principle adopted was that France should retain certain detached pieces of foreign states within her own frontier (such as Mühlhausen, Montbéliard, and the Venaissin), while the line of frontier was extended so as to include certain detached fragments belonging to France before 1792, such as Landau, Mariembourg, and Philippeville, as well as Western Savoy with Chambéry for its capital. She was moreover allowed to regain all her colonies except the Mauritius, St. Lucia, and Tobago. The Spanish portion of San Domingo was restored to the Spanish government. Holland was placed under the sovereignty of the house of Orange, and was to receive an increase of territory; so much of Italy as was not to be ceded to Austria was to consist of independent sovereign states; and Germany was to be formed into a confederation. Finally an European congress was to meet at Vienna in two months' time "to regulate the arrangements necessary for completing the dispositions of the treaty". At the same time secret articles provided that the disposition of territories was to be controlled at Vienna by Austria, Great Britain, Prussia, and Russia; that Austria, was to receive Venice and Lombardy as far as the Ticino; and that the former territories of Genoa were to be annexed to Sardinia, and the late Austrian Netherlands to Holland.