This paper presents a Relation, written in Italian and by an unknown author in Venice, referring to the earthquake that occurred on April 6, 1667 in the ancient city of Ragusa, now Dubrovnik, Croatia, a city that then had a great economic and cultural importance in the Adriatic and Mediterranean. This city was visited by the Venezuelan Francisco de Miranda (1750-1816) during the month of April 1786, on the 119th anniversary of the event and before continuing his journey through Greece and Turkey. The manuscript that was copied by Miranda and rests in the archive of his Travel Diary, constitutes a Relation of the events that occurred during this natural phenomenon of such outstanding relevance in European historical seismology. A seismological analysis of the earthquake is presented, based on the elements derived from the Relation, in contrast to other documentary sources; the impact and the main seismogenic characteristics of the earthquake are also analyzed. As an important figure of the Age of Enlightenment, Francisco de Miranda's interest in natural phenomena stands out, which in this case, led him to copy and preserve this document, which constitutes an important source of historical seismological information.