Passage: In 1815 the Congress of Vienna fully re-established Swiss independence and the European powers agreed to permanently recognise Swiss neutrality. Swiss troops still served foreign governments until 1860 when they fought in the Siege of Gaeta. The treaty also allowed Switzerland to increase its territory, with the admission of the cantons of Valais, Neuchâtel and Geneva. Switzerland's borders have not changed since, except for some minor adjustments.

Question: What year did the eminent countries of Europe certify Switzerland as an impartial entity?
1815