The Monastery of Santa Maria d'Alcobaça, north of Lisbon, was founded in the 12th century by King Alfonso I. Its size, the purity of its architectural style, the beauty of the materials and the care with which it was built make this a masterpiece of Cistercian Gothic art. The church and monastery were the first Gothic buildings in Portugal, and, together with the Monastery of Santa Cruz in Coimbra, it was one of the most important of the mediaeval monasteries in Portugal. Due to its artistic and historical importance, it was listed by UNESCO as a World Heritage Site in 1989.