Henry of Eppenstein, duke of Carinthia, donates his castle "in the place that is called Ruvoyn" to the Church of Aquileia.
Item instrumentum qualiter dux Henricus donavit ecclesie Aquilegensis castrum suum situm in Comitatu Istrie in loco qui dicitur Ruvoyn, anno MCII.a
a) seq. sub signo..(S) add. B.
Likewise, a deed by which Duke Henry donated to the Church of Aquileia his fort situated in the County of Istria in the place that is called Ruvoyn, in the year 1102.
There has been much confusion and unanswered questions regarding this line in Istrian historiography.
First, a mistake was made by Pietro Kandler ("Sulle varie popolazioni dell'Istria, L'Istria, vol. 7/51 (1852): p. 234), who erroneously dated the donation to 1002 instead of correctly to 1102.
Carlo de Franceschi (L'Istria: Note storiche, p. 99) corrected this mistake, but Kandler's erroneous dating was taken over by Bernardo Benussi (Nel medio evo, p. 291) who thus believed that the donation was made by Henry, the duke of Bavaria and the future emperor of the Holy Roman Empire. Due to Benussi's immense popularity, this erroneous dating has dominated Istrian historiography.
With the correct dating established, the duke in question can only be Henry of Eppenstein, the duke of Carinthia and the brother of Ulrich, the incumbent patriarch of Aquileia.
Moreover, the motive of the donation also becomes much clearer. Namely, between 1101 and 1102 several donation charters were issued to the Church of Aquileia bestowing land and possessions in Istria (see them here, here, and the most important one here). Thus, the donation was part of a plan to build up the secular lordship of the Patriarchate of Aquileia in Istria. The plan was enacted during the height of the Investiture Conflict in which House Eppenstein and the Church of Aquileia stood firmly with Emperor Henry IV whereas House Spanheim, under whose influence was Poppo III, the son and heir of Ulrich I, the late margrave of Istria, supported the reform papacy and Pope Gregory VII. Thus, the donations were to make sure that the possessions of late Margrave Ulrich do not fall into the hands of Poppo III's heirs and, indirectly, under the influence of the inimical House Spanheim. Henry Eppenstein's donation only rounded up the possessions donated in 1101 and 1102 by Ulrich II, Poppo III's brother who remained loyal to the Empire (see the donation charter here).
This historical context also sheds much-needed light on the correct location of the "place that is called Ruvoyn."
Namely, the first and the most logical conclusion would be that the toponym in question refers to Rovinj. This, however, cannot be as lordship over Rovinj was disputed by the Bishopric of Poreč and the Patriarchate of Aquileia as both competitors resorted to forging historical documents to "prove" their rights over this town. Had Duke Henry indeed donated Rovinj, there would be no such dispute and the patriarchs of Aquileia would not have to forge any document.
A much more logical conclusion, reached already by Kandler back in 1852, is that the toponym Ruvoyn refers to Petrapilosa which was also called Ravenstein: "ed ecco Ruvin [recte Ruvoyn], cangiato in Rauenstein per affinità di suono, e questo in Pietra-pelosa per traduzione (che esattamente suonerebbe Pietra-scabra o Pietra-ruvida)" (Kandler, op. cit., p. 234).
Indeed, if one compares the possessions donated by Ulrich II in 1102 (see the map here), Petrapilosa would fit the geographical region that was meant to become the basis of Aquileian lordship in Istria. Therefore, this opinion, although intermittently disputed (Camillo de Franceschi, "Mainardo conte d'Istria e le origini della Contea di Pisino," Atti e memorie della Società istriana di archeologia e storia patria 38 (1926): p. 37 argued in favor of Rovinj for example), remains dominant in Istrian historiography.
There is one problem though: Kandler postulated that Petrapilosa was called Ravenstein in documents prior to 1400, but this statement is not supported by primary sources. Namely, Thesauri clartias does mention a castrum de Ravenstayn (ed. Bianchi, n. 448, pp. 205-6 and n. 1359, p. 392) but this toponym refers to castle Ravistagno in Montenars in Friuli, not to Petrapilosa or any place in Istria. Thus, Kandler's original argument stands on very shaky foundations.
Another possible interpretation hearkens back to equating Ruvoyn with Rovinj. While it cannot be argued that the entire town of Rovinj was donated by Duke Henry of Eppenstein in 1102, it very well could be that only a fort in the district of Rovinj was in fact bestowed to the Church of Aquileia. The wording of the regestum supports such an interpretation: "a castrum located in the County of Istria, in the place which is called Ruvoyn". This fort in the district of Rovinj could be none other than Turnina (Ital. Torre di Boraso), an early medieval fortification built on a valuable strategic position (Josip Višnjić, "Turnina (Torre di Boraso): Carolingian Period Fortress and High Medieval Keep," in Fortifications, Defence Systems, Structures and Features in the Past, Zbornik Instituta za arheologiju 13 (Zagreb 2019), pp. 209-24).
There is a problem with this thesis as well: primary sources, albeit of Venetian provenance and from a much later period (first half of the 14th century), attest that Turnina was not an Aquileian property, but that it belonged to the Bishopric of Pula (see the edition of the source here). Nonetheless, in 1336 it was the patriarch of Aquileia who invested Sergius of Castropola with "medietas Turris Borasei cum omnibus suis pertinentiis, et cum mero et mixto imperio" (Kandler, Codice diplomatico istriano, vol. 3, doc. 658, p. 1139; a new critical edition of this document is forthcoming in FIM). Thus, it is quite possible that between the original 1102 donation and the 1330s the possession of Turnina got split between the Patriarchate of Aquileia and the Bishopric of Pula with the merum et mixtum imperium, that is secular authority including the right to shed blood and dispense justice in civil and criminal cases, remaining with the patriarchs of Aquileia who subsequently bestowed it to House Castropola, their principal allies and retainers in Istria. Venice, however, had all the motives to show that the rights over the important castle in the district of their town of Rovinj did not stem from the inimical Church of Aquileia, but from the bishops of Pula, a much less threatening enemy.
From the two possible interpretations, the second one has more support in primary sources and the toponym "Ruvoyn" is indeed very close to "Ruvignum", that is, Rovinj - Rovigno. Nonetheless, both theses are presented here before a more definitive conclusion is reached. The editor of this document and the author of these lines supported Kandler's thesis in his past works but now inclines more towards the Turnina-thesis.