Geyser Krepost (Fortress) is located on the right bank of the Geysernaya River, opposite the Shchel (Crack) Geyser. Until 1991, it was a pulsating spring. In July 1991, employees of the Geyser Observation and Study Association (GOSA) observed 2 eruptions with emissions of muddy water to a height of up to 6 m. In their report on the work, it is classified as a geyser and is called Fortress (Bryan, 1991). Until 2007, it operated mainly as a boiling spring. In 2007, after a landslide and the formation of a dammed lake, it began to operate as an unstable geyser with a fountaining height of up to 5 m, the period was 140-170 minutes, the duration of the eruption was 2-3 minutes (Leonov, 2017). In 2011, 2016, 2018, 2021 and 2023 the fountaining period was 2–2:40 hours, in 2015 — 12–16 hours, 2017 — 2–10 hours, in 2022 it did not work for 7 days, in 2023 it did not work for 4 days, in 2024 - not a single eruption was observed. According to our observations, the stability of its activity is not related to weather conditions.