1248

April 26 – The Gothic chapel Sainte-Chapelle is consecrated in Paris, France.
August 15 – The foundation stone of Cologne Cathedral is laid, after an older cathedral on the site burns down on April 30 (construction is completed 632 years later, in 1880).
August 25 – The Dutch city of Ommen receives city rights and fortification rights from Otto III, Archbishop of Utrecht, after it has been pillaged at least twice by a local robber baron.
November 23 – Reconquista: King Ferdinand III of Castile recaptures the city of Seville from the Moors, ending the Siege of Seville; this year also Prince Alfonso X of Castile takes the city of Alicante.
November 24 – In the middle of the night a mass on the north side of Mont Granier suddenly collapses, in one of the largest historical rock slope failures known in Europe.

King Louis IX of France launches the Seventh Crusade, setting sail with an army of 20,000 toward Egypt.
Pope Innocent IV grants the Croats permission to use their own language and script in liturgy (see Glagolitic alphabet).
Tallinn (Reval) converts from Riga law to Lübeck law.
Roger Bacon publishes the formula for black powder in Europe.
Approximate date – History of the Aztecs: The Mexica tribe, predecessors of the Aztec people, arrive at Chapultepec (in modern-day Mexico City).