Pula’s city walls are witnesses of both glory and frailty of this town. From the Twin until Golden Gates, the walls that were once a defense ring of antique and medieval Pula have been partially preserved. Traces of Roman walls from republican times, were found within fundaments or right next to walls from Histri time (Illyrian tribe living in Istria). At the beginning they were modest containing squared forts and towers each ten meters. Town walls from classical Roman times (end of 1st century BC until 2nd century AC) were much nicer, with round type towers even if they were completely non-functional because during that period the town itself wasn't endangered by attacks and thus needed no real protection. During the ascent of the Serenissima Republic (Republic of Venice) city walls have been demolished two times in 1150 and in 1243. According to writings of Pietro Kandler (a 19th century Austrian historian) Roman Pula defense wall had a diameter of 1600 meters, the town had 12 entrance doors, 7 of which on the southwest sea side, 5 on the northeast land side. Built in 11th century the Twin Gates have been preserved until nowadays as well as the Gate of Hercules from 50 BC during the birth of Coloniae Pietas Iuliae whereas the Triumphal Arch of the Sergi was placed behind the town entrance. During Venetian domination period the region had suffered from 40 plague epidemics, those from 1371, 1437, 1527 and 1631 left catastrophic consequences. City walls were decaying and there is a story about Jurisa Harambasa entering the town during night-time with 150 Uskoks (Croatian Habsburg soldiers) on the 29th April 1608 through holes and openings in the walls, burgling and taking with him to Senj a 4000 ducats worth catch. During Austrian governance in the middle of 19th century Pula's town walls were systematically and totally destroyed as part of the modernization process that required large open spaces.