The square owes its existence to the great Lisbon earthquake of the 1st of November 1755 and the fire that followed. On this spot, left empty due to natural disasters, a new regular city is built, as a result of reconstruction efforts coordinated by the Marquise of Pombal, the leader of the royal government.
Praça do Comércio appears on the place previously held by the court of the royal palace, Terreiro de Paço, a name still used for the square, with a side open towards the Tejo, the greatest river of the Iberian Peninsula. At 175 x 180 meters, the size of the square is huge, among the biggest on the European continent.
The history of the city is tied to Venice, but Rovinj was built much earlier, at the start of the 8th century, on an island separated from the land through a narrow canal. Much later, in 1763, towards the end of Venetian rule, the community silts the isthmus and the city is united with the mainland. Through a classic process of synoecism, a new system of markets takes shape right on the spot of the old canal. They are four in number, and the most important is Trg G. Matteottija. Most of the buildings here are from the 19th century, but they celebrate the past link of the city with Venice, even recreating the lion of San Marco on the city hall’s pediment. The main square of the city remains Trg Sveta Eufemije, found at the highest point on the hill. Free on three sides, it gazes out to the sea, dominated by the 60 meter campanile of the basilica, with the statue of Saint Euphemia at the top, rotating in the breeze.
Prešernov trg was a simple crossroads at the entrance of the medieval city, where, in 1646, a Franciscan monastery is built and which stands to this day. In the 19th century, the crossroads is paved and starts looking like an urban square. The end of the same century brings about a radical transformation, for, due to the earthquake of 1895, the old houses are replaced by Neoclassical and, later, by Sezession style buildings. In 1980, the Slovenian architect Edvard Ravnikar creates the current circle design of the pavement, which lends a special note to the square: a sun, on a granite background, with rays made of Macedonian Prilep marble. A triple bridge, Tromostovje, across the Ljubljanica, ties the square through Stritarjeva ulica to the old square of the city, found at the foot of the hill where the castle is, right next to the cathedral. The city square, Mestni trg, is dominated by a fountain built in 1751. The two squares, although they have not been planned together, and although they are each partly the result of later redevelopment, represent an unexpectedly coherent and suggestive urban whole.