Simssee Langstreckenschwimmen

The clear basin of the Simssee forms the last surviving remnant of the vast glacial lake that covered the Rosenheim valley at the end of the Würm glaciation. This quiet freshwater lake in Riedering, in the Bavarian district of Rosenheim, hosts the Simssee Langstreckenschwimmen, an open water swimming race held in its sheltered waters. {{h2:Strandbad Pietzing: the multi-lap course on Simssee}} The Simssee Langstreckenschwimmen is organized as part of the regional Alpen Open Water Cup circuit, bringing competitive open water swimmers regularly to the lake since 2022. The event is staged directly off the shoreline of Riedering at the Pietzing bathing area. Here, athletes step into the freshwater shallows of the lake, looking out across a wide, marked course designed to test both endurance specialists and tactical racers. The competition centers on an open 2 km loop laid out directly in front of the Pietzing beach. Swimmers select between three distinct race distances, taking on either a single 2 km circuit, a 4 km challenge, or the premier 6 km marathon distance.

In past editions, those tackling the three full laps of the 6 km contest experienced a classic Australian exit, climbing out of the water between laps for a brief run over land before diving back into the open lake. Scheduled in May, the race greets participants with the variable conditions typical of late spring in the Bavarian foothills. On warm days under sunny skies, the lake can be remarkably still and comfortably mild, with barely any wind-induced waves breaking across the smooth surface. However, mountain weather can turn abruptly following early-season cold snaps, dropping the water to a sharp, bracing chill. Such shifts demand careful preparation, rewarding swimmers who know how to manage their effort across cold water and changing mountain air.

Race day at the Pietzing bathing area

The Simssee swim on Sunday 17 May 2026 was the opening race of the arena Alpen Open Water Cup. A few days before the 2026 race the organisers reported that the Simssee had reached 20 °C (68 °F) in a spell of fine weather, before a cold snap brought it down to nearly 16 °C (61 °F). On race day the water was around 16 °C (61 °F), smooth and calm under sunshine, and more than 160 swimmers came to Pietzing although a wetsuit requirement had been announced in advance. The 4 km distance was swum on a triangular course 2,000 metres long. The Badeplatz Pietzing has changing rooms, toilets, showers, a kiosk, a water rescue service and a gently sloping gravel beach. The bathing area at Pietzing has a well-kept lawn and a small standing area about 30 metres wide close to the shore.

Simssee: the deep basin of the ancient Rosenheim Lake

As the sole surviving basin of the ancient Rosenheim Lake, the Simssee covers a surface area of 6.49 square kilometers. Its submerged topography plunges to a maximum depth of 22.5 meters, holding a vast volume of water within its post-glacial hollow. Because of the depth and capacity of the basin, the lake's water renewal time is exceptionally long, taking approximately one and a half years to completely replenish its volume. A ring of soft hills encloses the shoreline, sheltering the lake surface and preserving extensive natural reed beds along its edges. Near Pietzing, the Fellbach stream empties into the Simssee over a wide alluvial fan. The Angerbach originates northwest of Söllhuben and flows along ditches across the meadows before discharging into the southern part of the Simssee through an alluvial fan near the village of Beuerberg. In the municipality of Riedering, the Labenbach rises at the edge of the village of Moosen and meanders through the forest towards the northwest, eventually entering the Simssee across its own alluvial delta.

The southern nature reserve and the Sims outflow

The Simssee and its surrounding high and low moors have been designated as a protected landscape area since 1963, encompassing a 257-hectare conservation zone of untouched reed and shore belts. In 1993, the southern shore of the lake was granted further protection as a designated nature reserve, keeping human development away from its sensitive banks. From the calm waters of this southern sanctuary, at an elevation of 470 meters above sea level, the Sims river begins its journey. The river runs directly through the protected wetland reserve and winds into the dense woodlands of the Lauterbacher Filze. The Röthbach begins its journey at the Tinninger See, flowing as the Seebachl in its upper course until reaching the Sprenger Bächlein, where it receives the Aichach tributary east of Thansau before sweeping north in an arc to meet the Sims.

The Sims then joins the Rohrdorfer Achen, a river that rises in the Chiemgau Alps, flows north as the Weißenbach to join the Aubach, bends west toward Achenmühle, and runs parallel to the Inn before emptying into it at Stephanskirchen.

The moor lakes and swimming spots around Riedering

The 57-hectare Hofstätter See is bordered by natural moorlands. Swimmers find two official bathing grounds here: a modest beach on the northern shore and an expansive swimming area along the eastern shore of its southern basin. A 300-meter-long wooden boardwalk traverses the open moor at one end of the lake, giving visitors an intimate path over the protected peat bog. The Hofstätter See naturally feeds the adjacent Rinssee, a shallow lake nestled into the Alpine foothills of Upper Bavaria. Documented in historical records under the name Runssee as early as 1326, the lake provides an easy-going swimming destination with a kiosk and a dedicated bathing lawn at its northern end.

In the nearby municipality of Söchtenau, the Siferlinger See covers six hectares as a quiet moor lake in the Chiemgau region. The lake briefly made headlines in late August 2016 when the sighting of a 1.50-meter-long constrictor snake prompted local authorities to issue a swimming ban. The situation was swiftly resolved on September 3, 2016, when the escaped yellow anaconda was successfully captured without incident and safely transferred to a specialized reptile rescue center in Munich, returning the moor lake to its natural peace.