This is the largest confessional Catholic church in the Borgo Teresiano, the area of Trieste which backs onto the sea and which was restructured by the Austrian Empress Maria Theresa. It is the biggest in the city. Work on the church began in 1828, and it was finished in 1849. It is in a perfect location, not far from Piazza dell Unità d'Italia and the canal. This position was purposefully chosen by the Habsburgs to facilitate commercial trafficking. The church is built in a neoclassical style, and has a façade with six ionic columns which support a tympaneum and an attic decorated with statues of local martyrs. There is an eliptic cupola at the center of the construction. The linear simplicity of the façade resembles Roman temples, and the Pantheon in particular. The icons inside the church were financed by local patrons Pietro Nobile and Domenico Rossetti, and were painted by German and Venetian artists. The semicircular apse is decorated by a fresco representing Christ's entrance into Jerusalem, and is by Sebastiano Santi. The six altarpieces are also interesting and are painted in a rather unusual way. The Church can be visited before or after mass.

The Orthodox Serb community has been present in Trieste for many years, and has become well-integrated into the city's social structure. The San Spiridione Church was built over an already existing structure, which dated back to 1751. The old building was demolished after the Serb's separation from the Greek Orthodox community in around 1861, and the building work started on the current church (designed by the Milanese architect Carlo Maciacchini) which was finished in 1866. The San Spiridione is built in a Neo-Byzantine style, with mosaics, bell towers, and cupolas which are typical of Eastern churches. The mosaics were designed by the Milanese painter Giuseppe Bertini, and were built in Venetian workshops. The windows are by Pompeo Bertini, while the statues on the façade are by Emilio Bisi. The interior, in the form of a Greek cross, is full of light and gold, and oil paintings by Bertini which imitate the mosaic. There are four icons with precious silver decoration which were made in Moscow, and another two large icons and a painted cross on the altars in the Presbyterian which is off limits to the public. Votive lights and candles give the church a warm and welcoming feel. At the entrance to the church you can see a lamp which was donated by Tzar Paul I Romanov when he visited Trieste in 1782. Trieste's Orthodox Serb community is the largest in Italy, mainly due to its extreme proximity to the ex-Yugoslavian borders.

Just a 20-minute walk from Piazza dell'Unità d'Italia, this cathedral is a symbol of Trieste. It was built in 1300, when two, pre-existing basilicas were merged, forming the vast, central nave. There is a beautiful sandstone façade and a bell tower that was built in 1337. There are Byzantine mosaics in the enchanting interiors and a 13th-century chapel enclosed in a rich Baroque railing. The right nave is the chapel dedicated to St Justus, and the Bourbons of Spain are buried in the crypt. Admission: Free.

The Anglican church was introduced to Trieste after the wishes of Emperor Francis I of Austria in 1821. He instructed the master builder Giacomo Fumis to build a church where Anglicans could worship. It was built in the old part of the city at the end of Via San Michele. It is in front of a beautiful garden which has recently been restored. The castle and cathedral of San Giusto are only a few hundred meters away. The church is based on an ancient model and uses Greek architectural styles. It has two doric columns and a pronaos. Inside, there is a single nave and the decor is simple and sober. The church has recently been restored and it is now used by the council for meetings and cultural activities. The small Anglican community of Trieste meet every second Sunday of the month to celebrate the eucharist. This is held at 5p.