Even today the ground-plan of Porec reveals the typical geometric pattern of a Roman castrum; the decumanus ("main road") has preserved the character of the main road even today. In the 6th century the complex of St. Euphrasius' Basilica was built.
In the following centuries the town suffered a decline; it was renovated at the end of the 12th century; in the 13th century the town walls were reinforced, and in the 15th century, facing the Turkish threat, the town erected a new fortification system.
In the 18th century the town walls, having lost their function, gradually decayed. In the 19th and 20th centuries the construction of overdimensioned buildings, particularly by embanking the south-western part of the peninsula, where a hotel was built, disturbs homogeneity of the urban part, and a new centre of the town has developed on the eastern part, outside the town walls.

From the coast, the former Roman cardo leads to Matija Gubec Square. St. Maurus Street extends to the right of the square, containing a Gothic three-storey building from the 15th century on the southern part, a palace in the mixed Romanesque and Gothic styles in the north, and a two-storey Romanesque house, called the House of Two Saints, with two Romanesque reliefs of saints at the first floor level. Northwards from Matija Gu--bec Square one can reach the former decumanus (Dekumanska Street).
A Romanesque house, annexed in the 15th century (Gothic double windows), stands at the north-eastern corner of the intersection of the cardo and the decumanus, and next to it a Gothic palace from the 15th century (brackets shaped as lion's heads, the characteristic balcony).
A Gothic house from the 15th century stands on the opposite, southern side of the decumanus.
A 15th-century Gothic palace rests at the north-western corner (corner double windows), followed by a row of late Gothic palaces from the 15th century. The so-called Romanesque House, with outer staircase and a wooden balcony (exhibitions) lies further west, isolated from the rest.
Marafor Square is located where the ancient Roman forum used to be; the ruins of the Temple of Neptune from the 2nd century lie on the western side of the square. The forum's original pavement has been preserved along the northern row of houses on the square.
From Marafor Square, the way leads through Gunduliceva Street to the former Franciscan church (beginning of the 14th c.), which was horizontally partitioned in the second half of the 19th century, and the Istrian Diet re-sided in the hall on the first floor which was later tur-ned into an exhibition hall.
Passing northwards through the Ca-r-do, one re-ac-hes Euphrasius Street, with the Canon's Residence from 1251, a representative Romanesque se-cular building (Ro-man-e-sque double w-in-dows, portal and niches with inscriptions) - today the Parsonage.

A narrow passage leads west of the Canon's Residence to the complex of Euphrasius' Basilica (mid-6th c.), consisting of the church, atrium, baptistery and the former palace of the diocese. Being richly decorated and well preserved, the whole complex represents one of the most important monuments of the Byzantine art. The first sacral object erected on this location was the so-called Maurus' Oratory built in the second half of the 3rd century (fragments of the mosaic have been preserved). After the Edict of Milan in 313, a public church was built on this location, with its area doubled in the 4th century; one of the rooms was used for the service and the other represented a martyrium (where the relics of the Porec martyr, St. Maurus, were kept). A large three-nave building was erected there in the 5th century. The bishop of Porec, Euphrasius, had a splendid three-nave basilica built on its foundations.

A quadrangular atrium with Byzantine capitals of the columns stands in front of the church entrance. The atrium is ringed by a roofed-over portico on all the four sides, which houses a collection of stone monuments ("lapidarij"). The western side of the atrium includes an octangular baptistery, which leans on the 16th-century bell tower. The northern part of the complex is sealed off by the building of the former diocese, whose ground-plan originates from the 6th century but was reconstructed on several occasions. The Basilica has three naves, the central one being elevated. In the interior, the naves are separated by 18 columns with various capitals; the imposts above the capitals are decorated with medallions bearing the Bishop Euphrasius' initials. The stuccowork on the arches between the columns on the northern side has been preserved in its original form. The central nave ends with a deep apse, in front of which is an elevated sanctuary, separated from the rest by stone slabs with reliefs. The altar is decorated with a gold-plated antependium from 1452. Bishop Otto's ciborium from 1277 (the capitals of the columns originate from the 6th-century ciborium) is placed above the mensa. The baldachin of the ciborium is decorated with mosaics (the Annunciation, medallions with imprints of the Porec martyrs). The apse is adorned with rich mosaics, a masterpiece of the Byzantine art. The semi-dome features the Mother of God on the throne, with two archangels and figures of Istrian martyrs; the central figure in the group to the left is Bishop Euphrasius with a model of the church in his hand, his brother Claudius next to him, and between them a boy, the son of Claudius. The lower part of the mosaic depicts the Annunciation, the encounter of Mary and Elisabeth as well as three separate figures (Zachary, Archangel Gabriel and John the Baptist). A strip covered by marble plates with mother-of-pearl and multicoloured stone incrustations is placed below it. The back part of the apse's semicircle accommodates an elevated bishop's throne. Twelve medallions adorn the arch of the apse, representing portraits of the saints, with the medallion with a symbolic presentation of Christ as a lamb in the centre; the front wall of the apse features the following composition: Christ in the Sphere and six apostles on each side (the mosaic was damaged in the 18th century, restored in 1891). A preserved part of the original mosaic decorates the northern apse. The floor of the northern nave is formed of two layers of mosaics; the lower belonging to the 4th-century basilica, and the upper to the church from the 5th century. The door in the northern wall leads into a corridor and further to the sacristy which was annexed in the 15th century. The same corridor leads through the 13th-century passage and an elliptical antechamber to the three-foil memorial chapel with the crab of St. Maurus dating from the 1247. The apse on the south contains a preserved fragment of the original mosaic; the fragments of mural paintings from the 15th century. The ceiling from the 15th century has been recently restored. The southern wall has three chapels, of which the western was annexed in the 17th, and the eastern attached in the 19th century. The area between them was recently turned into a chapel; the central chapel contains choir stalls from 1452; the western chapel is decorated with a large polyptych by Antonio Vivarini from 1440, and a composition of The Last Supper (by J. Palma the Younger) and Christ in the House of Matthew and Martha (Francesco Bassano's workshop).

From St. Euphrasius' Basilica, the way leads southwards to the Decumanus. The representative palace Sincic from the 17th century, now the Museum of the Porec Region, stands at the south-eastern corner of the crossroads.
By walking along the Decumanus one reaches an exemplary Gothic palace from the 15th century (with a Gothic triforium on the front and a Renaissance portal) and, further down the pentagonal tower from the 13th century (restored in the 15th c.), the only preserved part of the former town gates. Joakim Rakovac Square lies at the end of the Decumanus as well as the church of St. Mary dating from the 18th century. Aldo Negri Street leads further to the round Venetian bastion from the 15th century.

The castle on the islet of St. Nicholas, erected in 1886, was turned into a hotel. The round tower from 1402 is one of the oldest preserved light-houses on the Adriatic.

Museum of the Porec Region (housed in the Sincic Palace) has a collection of stone monuments ("lapidarij"), an archaeological collection, furniture, paintings and ethnographic artefacts. In 1974 the Collection of the Porec County was set up, comprising about 40 exhibits, the most important of them being mosaic fragments (the oldest dating from the 3rd c.), crosses (13th c.), and several altar paintings (15th- 17th c.) as well as choir stalls.