Historical Evolution of Topana Fortress
The central and highest part of Topana Fortress was constructed during the 13th and 14th centuries when it was under the control of the noble Nelipić and Kosača families. Over the centuries, the fortress underwent numerous renovations, particularly during its time as an administrative center under Ottoman rule, following their conquest of Imotski in the late 15th century. The fortress served as the seat of the local kadi (judge) and civil governor.
After nearly 230 years under Ottoman rule, the fortress was captured by the Venetians in 1717, following a fierce bombardment that led to the Turkish retreat to Ljubuški and Mostar. The victory was celebrated on August 2, the Feast of Our Lady of the Angels, which remains the official day of the city of Imotski. Following the Turkish withdrawal, Venetian builder Ivan Macanović was commissioned to repair the fortress, restoring its main entrance and walls. However, with the end of Turkish threats, the fortress gradually lost its strategic importance and was abandoned by 1816, beginning a slow decline that was exacerbated in the early 20th century when a water reservoir was built on its highest plateau.
The fortress, irregular in shape to match the natural contours of the cliff on which it stands, stretches approximately 40 meters in length and is built on several levels. The visible remains date from the 14th to the 18th centuries, although earlier layers have been archaeologically preserved. The fortress is naturally protected on three sides: two by Blue Lake and the third by a dry, deep sinkhole (Jelavića or Gospin Dolac), now home to the town’s football stadium. The southern wall, which was more accessible, was fortified with buttresses as an extension of the rocky cliff.
Architectural Highlights of Topana
The upper part of Topana Fortress is divided into two sections: the higher section, with an entrance on the northeast corner where residential spaces, water cisterns, and dungeons were located; and the lower section, with the main entrance, above which was the priest’s residence and a small chapel dedicated to Our Lady of the Angels from the 18th century. The lower fortress, located on the southern side, was defended by a wall with a round tower, partially preserved to the left of the main entrance, and wooden palisades.
Blue Lake: Imotski’s Natural Wonder
Close to the fortress, on the very edge of Imotski, lies Blue Lake, a natural marvel known for the striking azure color of its waters. The lake is kidney-shaped, stretching about 800 meters in length from northeast to southwest, with a width varying between 250 and 400 meters. The depth of the sinkhole has been measured several times, with the southern edge being the lowest at 386 meters above sea level, while the northern edge reaches up to 527.7 meters. The water level fluctuates significantly, usually reaching up to 329 meters above sea level during rainy periods, giving the lake a depth of about 90 meters. However, the lake’s depth can vary drastically, from complete dryness to its greatest recorded depth of 147 meters when it overflowed—a phenomenon unlikely to recur due to an earthquake in 1942 that widened the underground drainage cracks, leading to more frequent drying of the lake in early autumn during dry years.
The process of sedimentation is particularly visible on the lake’s northern side, with increased sedimentation on the southern side following the 1942 earthquake, which caused the collapse of Vidilica, sending large blocks of stone tumbling into the lake. All of Imotski’s lakes, including Blue Lake, are connected to a network of underground fissures, through which water rises under hydrostatic pressure, increasing the lake’s water level. These fissures, varying in size, typically open at or near the bottom of the lake. When Blue Lake dries up, these openings can be seen as tiny craters resembling extinct volcanoes.