Archaeologists working off the coast of southern Greece have uncovered new evidence of an extensive ancient harbor complex submerged near the archaeological site of Asini in the Argolis region.
The discovery sheds light on a sophisticated maritime installation that appears to have been used and modified over several historical periods, highlighting the long-standing strategic importance of the area.
Underwater excavation reveals layered construction
The latest fieldwork took place between late September and early October 2025 in shallow waters east of the well-known archaeological site, near the modern coastal area of Tolo. The region is characterized by a naturally sheltered bay and a prominent hill that made it an important settlement location from prehistoric times through to later historical periods.
The investigation forms part of a five-year research program that began in 2022, following a pilot study conducted in 2021. The project is a collaboration between Greek and Swedish archaeological institutions, including Greece’s Underwater Antiquities authority and academic partners from Stockholm and Gothenburg universities.
Artificial platform at the heart of the harbor
Between 2021 and 2025, researchers mapped a large artificial structure located just offshore. At its core is a broad platform built in shallow water, which is believed to reflect advanced ancient engineering and deliberate coastal planning.
What initially appeared to be a simple scatter of stones has now been identified as a structured construction with distinct architectural features. High-resolution 3D modelling and underwater observation revealed carefully arranged stone elements, including block-like formations that suggest intentional design rather than natural accumulation.
Evidence of multiple construction phases
To better understand the structure’s timeline, researchers partially removed stone material from selected areas and recovered only a small number of ceramic fragments. These findings suggest that the harbor complex developed in several stages rather than being built at once.
Square-shaped structures found on the platform are believed to have served as foundations for wooden caissons filled with stone. Over time, the wood decayed, leaving only the stone cores behind. Scholars interpret these as later additions built atop an earlier base structure, indicating continuous adaptation of the harbor.
Roman-era origins and long-term use
Previous analyses suggest that the main platform, particularly its western section, likely dates back to the Roman period. This conclusion is supported by pottery fragments recovered from within the structure.
Researchers believe the platform originally functioned as a pier extending above sea level. As water levels gradually rose over time, parts of the installation became submerged. To maintain its use, ancient builders appear to have constructed new wooden-based extensions directly on top of the sunken remains, ensuring the harbor continued to operate for loading and unloading goods.
Ongoing international research
Further study of the site continues through a detailed analysis of the 3D models and material findings from all excavation seasons. Researchers hope this will clarify the full evolution and function of the harbor and its role in regional maritime activity.
The project is jointly led by Greek and Swedish experts, including underwater archaeologists and maritime specialists
