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 this city is tied to Venice, but Rovinj was built much earlier, at the start of the 8th century, on an island separated from land by 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. Unobstructed 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 to the medieval city, where, in 1646, a Franciscan monastery was built and remains to this day. In the 19th century, the crossroads was paved and started to resemble an urban square. The end of the same century brought about a radical transformation, as an earthquake in 1895 resulted in the old houses being replaced by Neoclassical and, later, Sezession style buildings. In 1980, the Slovenian architect Edvard Ravnikar created the current circle design of its 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, next to the cathedral. The city square, Mestni trg, is dominated by a fountain built in 1751. The two squares, although they were not planned together, as each was partly the result of later redevelopments, represent an unexpectedly coherent and suggestive urban whole.