The Great parish church Santa María la Mayor, which held the status of collegiate church until 1851, stands close over the Gothic market and the City Hall. The great bell tower and a small area in a corner of the epistle constitute the only remains of the former Gothic temple. It was ostensibly smaller than the current Baroque temple and it was facing west. It had three naves. The central one higher than the lateral ones. It had an ambulatory divided into four square streches and five triangular and absidal chapels with a square plan. All the temple was covered by a simple groin vault.
The tower was attached to epistle of the church. Currently it is not aligned and it is linked to the western strech of the stone cross of the Baroque temple. It was built during the first half of the 14th century and more works were done during the 16th century. It is believed the council initiated the works to rise a magnificent monument facing the Calatravos Castle and the power it represented.
The tower stands out due to its multifunctionality. It had a religious function (tower bell) and a militar one (it was used as a shelter). It is a prismatic tower, with a square plan and it was made using big ashlars whose angles had chamfered corners. The tower was strengthened half its height with a double buttress. It has four floors which in the outside facade are defined by cornices.
In the early 18th century it was decided to demolish the Gothic temple of Santa María la Mayor. The new Baroque temple was made up by the former bell tower and a new chapel known as Soledad which started to be built in 1698. After several interruptions it was finished in 1732. Gaspar Serrano was the master of the works and the paintings were made by Francisco Plano and his son Felipe. The stained glass windows were made by José Dueñas. This chapel was planned to be an independent building.
As for iconography is concerned, the interior decoration deals about the Passion of Christ, Solitude and Silence. The new decoration was probably finished by the end of the 18th century and it replaced Francisco Plano's paintings.
The Gothic temple started decaying at the end of the 17th century. In 1713 there was a fire in the altar which affected the column near the chorus. The column collapsed in 1735 and consequently a part of the nave collapsed too. The demolition of the temple responded to a desire to build a new temple with a higher capacity. Thus, in August 25, 1735, Tomás de Agüero, archbishop of Zaragoza approved the demolition of the church. Domingo de Yarza was in charge of the new design of the temple. Silvestre Colás and Miguel de Aguas continued the works in 1736. From 1737 to 1749 Miguel de Aguas was the only responsible of the works. When he died in 1749 Anastasio Aznar succeeded him. Most part of the works were done by 1757. In the early 1780s it is believed they were finished.
This church follows the same plan as the temple El Pilar in Zaragoza: a rectangular plan made up of three naves of the same height, a cross stone, lateral chapels and four towers in the angles. Although the temple El Pilar was the paradigm of the religious Baroque architecture in Aragon between the years 1675 and 1765, the collegiate church in Alcañiz brought this style to the rest of the county El Bajo Aragon. Felipe Sánchez designed the project which was used to build El Pilar between 1674 and 1678. This model was used in many churches in the county.
The main facade of the church is flanked by two high towers and it has a great arch in its facade. It is a facade-alterpiece and it conveys the Baroque idea of movement and a sense of harmony and beauty. Different images are illustrated there: Santa María, San Pedro, San Pablo... This facade is structured into three sections arranged in a pyramid.
The central nave and the arms of the cross stone are covered by a barrel vault. The lateral naves are covered by a groin vault, and the lateral chapels by oval and circular domes. The cimborio of the central dome is made of brick. It has an octogonal ground plan and it is decorated with geometrical motifs.
As for the masterpieces, we can mention the alterpiece and others which are kept in the sacristy. The main alterpiece is a work of Tomás Llovet (1800-1805). After the war it suffered important modifications. The damages deteriorated the figures. In the sacristy there is an interesting set of Gothic pannels which are thought to be the work of Domingo Ram, one the most important painters of pannels in Aragon by the end of the 15th century. The masterpieces which are kept are pannels representing the Virgin Santa María Magdalena, San Jerónimo, San Miguel, San Gregorio, San Pablo and the Virgin El Rosario. In this same place there is a set of pannels thought to be done by the Master of Alcañiz. They date from the first two decades of the 16th century. They represent San Cosme, San Damián, Santa Catalina de Siena, Santa Apolonia, San Jerónimo, San Pedro, San Blas and an Epiphany.