Kostanjevica includes at least three cultural and spiritual experiences. It is a place of ecclesiastical art and a center of spirituality (church and monastery); it is a historical center (the Tombs of the Bourbons) and cultural center (the monastery library). The Franciscan Fathers have maintained these treasures for almost 200 years.

In 1985 the whole complex of Kostanjevica (the monastery and its library, the Bourbon tombs and the parish church) were declared a cultural and historical landmark. As such, they preserve a part of the Slovenian national cultural heritage.

In addition to various legendary accounts about the founding of the church, there remains one historical fact. In 1623 Count Mathias Thurn had a small church built on this spot. After it was completed, an image of Mary was installed in the church so the faithful could meet in prayer and for liturgical devotions. The Count also had a small monastery built next to the church. Among the first caretakers of the church and the monastery were the Carmelites who for 134 years beautified and enlarged both buildings. In 1781, when Kostanjevica was at the height of its renown, the Carmelites were expelled by a decree of Joseph II. At their departure they left nothing behind. The monastery and the church were closed for nine years. In 1811 Kostanjevica was entrusted to the care of the Franciscans who have managed it to this day. After the church was destroyed in World War I the Franciscans had it rebuilt in 1924 – 1929. The stucco was redone and the church was again resplendent in its former beauty.

The image of Mary with the baby Jesus is situated in the middle of the main altar. Around it is a frame of golden rays. This fresco of our merciful Mother, known also as Our Lady of Kostanjevica, was made by Leonardo Rigo. The fresco of The Coronation of the Blessed Virgin Mary on the ceiling of the church was painted by Giovanni Moro, a Friulian artist.

The stone memorial tablets in honor of the dead are distinctive in this church of Kostanjevica and indicate the closeness which the nobles of Gorica felt towards this place.

The monastery has a library which was named in honor of Fr. Stanislav Škrabec (1844 – 1918), the greatest Slovenian linguist and grammarian of the 19th century, who lived here for more than 42 years.

The tombs of the last members of the French royal family of the Bourbons can be found in the crypt of the Church of Kostanjevica.