4 MP 2016 (Mistrzostwa Polski w pływaniu na wodach otwartych)

Four vast basins connected by narrow channels give Lake Ukiel more than twenty kilometres of steep shoreline. Here, in the Warmian-Masurian region of northeastern Poland, the Polish Open Water Championships gather long-distance swimmers for traditional freshwater marathon racing. Ukiel is the largest lake in the city, spreading across 412 hectares of open water. Its perimeter extends for 22.48 kilometres along high, mostly steep and forested banks, with an average depth of 10.6 metres and plunging spots that reach 43 metres. The expanse of the lake is naturally partitioned into four distinct basins: Gutkowskie, Przejma, Łupstychskie, and Olsztyńskie. Narrow waterways thread these basins together, known locally as Lwia Paszcza, Czarne Wrota, and Zakręt.

The lake drains through the Kortówka river and Lake Kortowskie, with its waters eventually joining the Łyna river. Not far from Ukiel's shores, the Likusy district of Olsztyn shelters another deep body of water, Lake Sukiel. Covering an area of 20.8 hectares with a water volume of 1,366,000 cubic metres, Sukiel plunges down to a maximum depth of 25 metres, mirroring the dramatic depths carved across this post-glacial landscape.

The Polish Open Water Championships on Lake Ukiel

The Polish Swimming Federation has organized the national open water championships without a break since 2013. After the earliest editions were staged at Kryspinów, the competition moved to Olsztyn, drawing competitors to Lake Ukiel alongside the regional swimming association and the municipal sports facilities of CSR Ukiel. Spanned across a weekend in late July, the championship schedule delivers two full days of racing. Individual distance events take place on Saturday, before Sunday welcomes team relay squads to the water. The programme features courses suited to different age brackets and marathon specialists, ranging from 1,000 metres up to 10,000 metres. Junior swimmers take on distances like 2.5 kilometres over three laps, while older categories contest five kilometres over six laps, 7.5 kilometres over nine laps, and the premier 10-kilometre test over twelve full laps.

Masters competitors have also competed on Lake Ukiel over a distance of 2,950 metres, testing their pacing around the designated turn buoys. A distinctive highlight of the weekend is the three-person relay over a 3-kilometre course. Instead of handing off a chip between legs, all three members of the team swim together as a tight unit from start to finish, with mixed squads required to field at least one female athlete. Working in tandem, swimmers draft tightly behind one another to slice through surface chop and maintain collective speed through the buoy turns. Championship rules uphold traditional open water principles: wetsuits are strictly prohibited, leaving every athlete to swim in standard textile costumes.

Federation regulations ensure full safety by mandating that races are called off if water temperatures drop below a strict threshold. At night, land cools more quickly than the lake surface, setting off land breezes that drift toward the water by dawn. Yet competitors frequently find the summer lake water warmer than the morning air, even if sustained effort over several laps brings the inevitable chill of open water. The event has seen memorable finishes: during a past women's 10 km race, national team swimmer Joanna Zachoszcz, preparing for the Olympics, reached the finish line alongside Justyna Burska, with the two club teammates crossing together hand-in-hand.

Downstream on Lake Kortowskie and the Kortówka

The water draining out of Lake Ukiel flows through the Kortówka river directly into Lake Kortowskie. This lake reaches a maximum depth of 17.2 metres, with an overall average depth of 5.9 metres. Its underwater basin is split into three parts: a northern basin measuring 15.7 metres deep, a central section reaching 6 metres, and a southern basin plunging down to 17.2 metres. Three forest streams feed into the lake alongside the Kortówka, keeping its water circulating steadily toward the Łyna. Lake Kortowskie holds an essential place in environmental history as the first lake in the world subjected to the Kortowski experiment. Begun in 1956, this pioneering technical reclamation method focused on rehabilitating the lake basin. Today, the western shore of Lake Kortowskie remains covered by forest, and the lake is classified as a bream lake.

Lake Długie and the primeval peat bog of Mszar

Lake Ukiel also shares an artificial connection with Lake Czarne and Lake Długie. With a shoreline stretching 4,080 metres, Lake Długie reaches a maximum depth of 17.3 metres and averages 5.3 metres across its bed. Hydrologically, it forms an enclosed basin with no natural surface inlets or outlets, exhibiting bradymictic conditions where water mass dynamics remain very limited. East of Lake Długie's northern bay lies the Mszar nature reserve, about three kilometres from the swimming venue. Established in December 1953 as a strict peatland reserve, it spans 5.24 hectares inside the Municipal Forest of Olsztyn. The reserve occupies a closed hollow that was once an open lake, now filled with a peat deposit averaging 13 metres in thickness.

At 115 metres above sea level, the peatland sits several metres higher than adjacent Lake Długie. It shelters fragile plant communities, notably bog-pine and peat-moss habitats including Vaccinio uliginosi-Pinetum and Ledo-Sphagnetum magellanici. Rare botanical specimens thrive here, including insect-trapping round-leaved sundews and long-leaved sundews nestled in damp moss cushions.

Olsztyn Castle and the Łyna riverfront

The drainage waters of the lake system eventually feed into the Łyna River, which has anchored the city since the Middle Ages. In 1334, a defensive watchtower was built along the riverbank. Between 1346 and 1353, builders erected Olsztyn Castle, surrounding the stronghold with defensive walls, a drawbridge, and a protective ditch connected to the river. In the early 16th century, the castle tower was reconstructed to reach a height of 40 metres. The castle famously withstood historic combat in 1521, when astronomer Nicolaus Copernicus directed the successful defense of the fortress during a Teutonic siege. The castle ditch remained part of the water landscape until 1845, when it was filled in and the bridge was replaced with a permanent levee.

Today, the river beneath the castle fortress is surrounded by public green spaces. Castle Park lies along the Old Town by the riverbanks, where four purple European beech trees with circumferences between 227 and 300 centimetres were declared natural monuments in 2017.