The study explores the historical city of Qalhat and the factors that led to its decline. While it is commonly believed that an earthquake caused the city's destruction, the researcher proposes an alternative hypothesis: that a natural disaster, such as a tropical cyclone or an extended period of heavy rainfall lasting several days, may have played a significant role in its ruin. To determine the true cause of Qalhat's decline, the study analyses translated Portuguese archival documents.

Using a descriptive-analytical methodology, the research traces the city’s historical development before the arrival of the Portuguese in the Arabian Gulf and examines its continued prosperity under Portuguese rule. A comparative approach is then employed to juxtapose these documents with the travelogues of Portuguese voyagers who visited Qalhat, to connect all these records with writings about the city of Qalhat, and to uncover the reason for the city’s disappearance from local narratives and Omani history books. Additionally, the study includes photographs of the city’s archaeological remains and its most significant landmarks.

Keywords: Qalhat - Portugal - Hormuz – Earthquake - Cyclone - Mails