A few kilometers to the north of Alcobaca is the wondrous building constructed in memory of an important battle, that of Aljubarrota in 1385 when Dom Joao I defeated the Castilians and ensuring two hundred years of virtual independence from Spanish Invaders.

When King Dom Fernando I died without an heir to the throne it was claimed by both his illegitimate brother Dom Joao I and Juan de Castile of Spain on behalf of his wife. On the 14th of August of that year the out numbered army of Dom Joao I commanded by the outstanding general Nuno Alvares Pereira faced the Spanish forces just south of the Abbey. It is said on the eve of the battle Dom Joao made a vow to construct an unforgettable church in memory of the Virgin Mary should he succeed the next day.