As a group, these churches represent an especially pure and consistent example of pictorial art and architecture in the Lombard Romanesque style. The two churches in Taüll were declared national monuments in 1931, Sant Joan de Boí and Santa Eulàlia d’Erill-la-Vall in 1962, and the rest of the churches in 1993. It is in this group of exceptionally well preserved rural churches that the largest concentration in Europe of Romanesque art is to be found. Criterion (iv): The Churches of the Vall de Boí are an especially pure and consistent example of Romanesque art in a virtually untouched rural setting. Now, only Santa Maria at Durro to some extent, and otherwise only Santa Maria, Cardet, which are distinctive in several other respects also, provide in their unconserved state a good idea of church development and an interior in late- and post-medieval times.