Wikipedia:Selected anniversaries/April 11
April 11: Juan Santamaría Day in Costa Rica.
- 1241 – Mongol invasion of Europe: Mongols led by Batu Khan and Subutai crushed the Hungarian army of King Béla IV at the Battle of Mohi near the Sajó River in Hungary.
- 1713 – The main agreements of the Treaty of Utrecht were signed in the Dutch city of Utrecht, helping to end the War of the Spanish Succession.
- 1888 – The Concertgebouw concert hall in Amsterdam, the Netherlands, was inaugurated.
- 1945 – World War II: American forces liberated the Buchenwald concentration camp near Weimar, Germany.
- 1979 – Ugandan–Tanzanian War: The Uganda National Liberation Army and Tanzanian forces captured Kampala, forcing Ugandan President Idi Amin to flee.
- 2002 – In a coup attempt, members of the Venezuelan military detained President Hugo Chávez (pictured) and demanded his resignation.