Stubacher Sonnblickkees (SSK) is located in the Hohe Tauern Range (Eastern Alps, Austria) in the upper Stubach Valley. The east-facing slope glacier extends from about 3050 m a.s.l. and covered 1.7 km² in the 1980s, shrinking to less than 1 km² by 2020. Due to its thin ice cover and complex subglacial topography, it shows highly irregular surface patterns without a distinct glacier tongue. Mass balance observations began in 1963 to test and refine early glaciological methods under complex topographic conditions. Logistic advantages included proximity to Rudolfshütte and hydrological data from the Weißsee reservoir operated by Austrian Federal Railways. Compared to the drier Ötztal Alps (e.g., Hintereisferner), the Hohe Tauern experience higher precipitation, offering valuable comparative insights into glacier–climate responses. A meteorological station operated at Rudolfshütte from 1961–1967, and since 1980 a climate observatory run by ZAMG and the Salzburg Hydrological Service has provided continuous long-term data. Direct annual mass balance measurements were conducted from 1964 to 1981, initially under the International Hydrological Decade (IHD) and later the International Hydrological Programme (IHP). Research was led by Heinz Slupetzky (University of Salzburg), later supported by the High Alpine Research Station (founded 1982). Early research focused on understanding how complex topography affects accumulation and ablation. Strong southerly foehn winds and northern storm events cause pronounced snow redistribution, leading to characteristic and persistent spatial accumulation and melt patterns. Mapping maximum snow depletion (AAR) became a key method for calculating total mass balance, especially given the absence of a simple equilibrium line. Over time, measurement density was optimized as spatial patterns proved consistent. Since 1981, regression analysis between specific net balance and AAR has enabled semi-direct mass balance calculations, supported by independent geodetic methods including photogrammetry, laser scanning, and modelling tools. The method was successfully tested on a comparable glacier in Canada, confirming its transferability. The series was reconstructed back to 1959 using aerial imagery, and to 1950 via meteorological correlations. Between 1965 and 1981, SSK gained approximately 10 million m³ of ice, resulting in glacier advance until the mid-1980s. Since 1982, however, the glacier has lost around 35 million m³ (by 2013), retreated about 600 m, and increasingly disintegrated due to rock outcrops and the formation of a proglacial lake. Continued runoff measurements (since 2002) and precipitation records allow estimation of the catchment water balance, with long-term mean runoff around 3,000 mm/year. SSK hosts one of the longest glacier mass balance series in the Hohe Tauern and worldwide. Today, monitoring is coordinated by the Hydrographic Survey of Salzburg and the Department of Geoinformatics (Z_GIS) at the University of Salzburg. The site is integrated into international monitoring networks such as LTER (Site Oberes Stubachtal) and contributes to global long-term ecosystem research and regional climate strategies (Salzburg 2050).