The charm of this square is truly indescribable, it overlooks the sea, surrounded by historic buildings, this is the place where the discovery of Trieste begins, its history, its people who work in the various public offices, its premises.

The castle of San Giusto is a fortress-museum located on the hill of the same name, in Trieste. As a historic residence, it was restored in the 2000s and used as a civic museum by the Municipality of Trieste, to which the structure has belonged since 1930. On the Lalio bastion, the Tergestino Lapidary was inaugurated on 4 April 2001, consisting of inscriptions, sculptures, bas-reliefs and fragments of Roman era architecture.

It was built in 1754-1756 by the Venetian Matteo Pirona, further digging the main collector of the salt pans, when these were filled in to allow the urban development of the city outside the walls. It was built so that boats could reach the city center directly to unload and load their goods. In its initial configuration, the canal was longer than it is today, and reached up to the church of Sant'Antonio. The terminal part of the canal was in fact filled in in 1934, with the rubble resulting from the demolition of the old city, thus obtaining the current Piazza Sant'Antonio. It is said that a small torpedo boat that had been moored there damaged and abandoned since the end of the war was also buried in the landfill, although from the photographs of the time, depicting the landfill work, no hull can be seen.

The Roman theater of Trieste is located at the foot of the San Giusto hill, in the center of the city, on the edge of the old city. At the time of its construction the theater was located outside the city walls and on the seashore, which at that time reached up to that area. On its steps, also built taking advantage of the natural slope of the hill, could accommodate, depending on the various sources, from 3,500 to 6,000 spectators. The construction of the theater is dated to the end of the 1st century BC and expanded at the beginning of the 2nd century AD. It was probably built at the behest of the Triestine Quinto Petronius Modestus, procurator and flamene of the emperor Trajan, mentioned in various inscriptions, who according to other sources instead only took care of the renovation works.

The Arch of Riccardo is, according to some sources, one of the Roman gates of Trieste; dating back to the 1st century BC, it was probably built under the emperor Octavian Augustus in the years 33-32 BC. The forms of the architectural decoration allow us to date the current shape of the arch to the Claudio-Neronian or perhaps Flavian age (50-75 AD). According to other sources, however, it is one of the entrances to the sanctuary of the Magna Mater. It is an arch with a single fornix, 7.2 m high, 5.3 m wide and 2 m deep. It has an upper crown, without decoration. On the sides there are two pilasters, of which only one is currently visible, with grooves surmounted by Corinthian capitals. The ceiling of the arch was decorated with coffers.

The Evangelical Lutheran church is a religious building located in Trieste, belonging to the evangelical community of the Augustan confession. Built in the 19th century to a design by Carl Johann Christian Zimmermann in German neo-Gothic style, the church is located in Largo Odorico Panfili, behind the Post Office building, in Borgo Teresiano. After the city of Trieste was declared a free port, the first five families of Lutheran merchants arrived in 1717, followed by others. The Lutheran church was designed in Wroclaw in 1870 in German neo-Gothic style by the engineer Carl Johann Christian Zimmermann and built under the supervision of the Trieste architects Giovanni Andrea Berlam and Giovanni Scalmanini and the architect Brisco from Wroclaw. Since this was an area where there were former salt pans, the ground had to be reinforced by planting over 200 25 meter long oak poles.

Designed by the architect Carlo Maciachini (1869), it stands on the site of the pre-existing church of San Spiridione from 1753. The architectural complex, located in the Teresiano village near the Grand Canal, reflects a Byzantine taste and is characterized by a dome which is the highest of the four bell towers, for the blue hemispherical caps and for the large mosaic decorations that embellish the external walls. The façade is adorned by nine large statues by the Milanese sculptor Emilio Bisi (1850-1920). The interior is richly decorated according to Byzantine canons, entirely adorned with oil paintings imitating mosaic. There is a rich iconostasis with four icons of great value: Saint Spyridon, Madonna with Child, Christ the King, the Annunciation. They are covered in gold and silver and were made in Russia in the early 19th century. Three altars are located in the presbytery. The large silver lamp that hangs at the entrance is a gift from Paul Petrovič Romanov, future tsar of Russia with the name of Paul I.

The archpriest church of Sant'Antonio Taumaturgo (commonly called the church of Sant'Antonio Nuovo), is the main religious building of the Borgo Teresiano and the center of Trieste. The project of the church dates back to 1808, but work only began in 1825. The facade of the building is characterized by six Ionic columns. Also on the main facade, in the attic, there are six statues sculpted by Francesco Bosa in 1842, depicting San Giusto, San Sergio, San Servolo, San Mauro, Sant'Eufemia and Santa Tecla. The church is located in the square of the same name, close to the Grand Canal. Until the mid-eighteenth century, a private chapel dedicated to the Annunciation stood in its place. After the concession by Antonio Rossetti to make access to the chapel public, it became insufficient given the large influx of believers. So it was decided to build a larger church, in baroque style dedicated to Sant'Antonio Nuovo.