The Church of the Assumption of the Blessed Virgin Mary was never destined to become a cathedral, even though the walls are evidence that the church has been here for centuries. It is situated beside the main intersecting Roman streets from east to west called decumanum, along the eastern periphery of the City walls and in the vicinity of the first port on the river Rječina.
In the first century, a public thermal complex was located on this site until the beginning of the 4th century, when a new one was built. On the south side of the church, archaeological explorations have revealed the area of a hypocaust, the hollow floor used to heat the air within the thermae. At the present time, it is preserved under the foundations of the surrounding edifices.
In the 5th and the 6th centuries, a part of the thermae was most likely transformed into an early Christian religious cult area. The findings of mosaics beside the church-tower as well as along its main forepart dating from late antiquity indicate that the forum, a City Square, was sited here with a plausible monumental public building.
Judging by the structure of part of the north wall, and the inscription on the bell-tower dating from 1377, a smaller church with a freestanding bell-tower existed throughout the medieval era. Its existence was documented for the first time in the 15th century, when it was extending towards the east and west, resulting in a monumental baroque three-nave edifice with a classic façade from the year 1842, with an embedded Renaissance rosette and a baroque portal, and a work of art on the gable by one of Vienna’s masters from the 1890s.
In the period between 1716 and 1726, the Orlando family initiated the most important renovation of the church by bringing artists and masters from Ljubljana for the construction of a new apse and altar. Under the influence of the Venetian baroque, the sculptor Jacopo Contiero from Padova built the main altar. The Altarpiece Assunta is a work by Rijeka`s painter Ivan Simonetti in 1852, as a replica of Tizian’s famous work. Giovanni and Leonardo Pacassi, Pasquale Lazzarini, Antonio Michelazzi and Sebastiano Petruzzi worked on the marble altars, whilst the altarpieces were primarily the works of Ljubljana`s painters Valentin Metzinger and Ivan Franjo Gladić. The works of art have the features of the gothic workshops that were active on the Hapsburgs territories.
The baroque stuccowork in the apse and the triumph arch is the work of Giulio Quadrio, their replicas dated from 1864 can be found in the remaining part of the church. Members of the brotherhood, patrician families and priests were buried beneath the church for centuries, but sepulchral slabs were only embedded in its northern wall since 1901. The Orlando family constructed a crypt as a tomb for themselves and the deans.
One of the most important events in the history of Rijeka was an earthquake in 1750. St Phillip Nerri’s altar was constructed as a vow, the altarpiece of which illustrates the town at the moment of the catastrophe. Another vow, St Rocco’s church, was built on the northern side of the square in the period of a severe plague in 1599, beside which a Women’s Benedictine Monastery was built in the middle of the 17th century. The great complex was demolished in 1914 and has similarly erased the Renaissance chapels of St Anton Opat and St Kuzma and Damien, which were annexed to the gothic church tower in the centre of the square.
The bell tower with Gothic characteristics arrived after all of the historical additions were removed from it, as a rare and preserved city monument from the Middle Ages, and it has a unique feature: a 40 cm slope, which is why it was called "The Leaning Tower". The cause of this distortion, which is the reason why there were several attempts to demolish the tower in the past, lies partially in the tower's Late Antique foundations and partially in the ground underneath it that is strongly affected by groundwater streams.