The basilica of Our Lady of the Assumption is the only medieval building in the park to have lasted until our own times, thanks in no small measure to the numerous restorations it has undergone.
The first documentary reference to the church dedicated to the Madonna was in 1203, but its origins are far older.
To determine the origin of this historic building is a question that has occupied scholars for decades. For a complete picture of the problem we recommend the studies of Giuseppe Cuscito, the most recent of which is the 2016 guide to “The Archaeological Park of Muggia Vecchia”.
It is not known exactly when a church was first built on the hill, but it is supposed that it could have had the role of a mother church, as the point of departure for the evangelisation of the territory.
Many elements of the liturgical furnishing are dateable to the C8th or C9th, like the plutei of the presbyteral enclosure and the white capital which crutch-like supports the mullioned window on the facade.
Characteristics of the period are precisely the interlaced decoration of those plutei typical of pre-Roman sculpture.
Their present arrangement is not the original, but is the result of a later restoration.
The circular ambo, the raised structure from which the biblical readings were delivered during the service, goes back to a period between the C10th and the C11th. It is surrounded by six balusters, besides a seventh which supports the lectern, and decorated with vine leaves whose original green colour can still be seen. At the sides of the lectern two masculine heads look towards the Faithful.
Very probably the building underwent a general restoration between the C12th and C13th.
It is to this period that the present church tower belongs, perhaps substituting one that may have stood on the southern flank, and also the present cycle of frescoes superimposed upon the previous one, of which there remains a faint trace of a drawing of a hand and a bust, discernible under the present drawing of Santa Caterina da Siena.