The Ravne Tunnel Complex in Visoko, Bosnia-Herzegovina, is a prehistoric underground network whose environmental conditions have been systematically monitored over a seven-year period (2018–2025). Using calibrated instruments, researchers conducted multiple measurements per week, selecting two representative datasets per year—typically one in winter and one in summer—for comparative analysis. Parameters recorded included concentrations of negative and positive air ions, ambient oxygen levels, gamma radiation, electromagnetic fields, temperature, humidity, and “life energy” levels. Values were consistently stable, with negative ion concentrations often reaching extraordinary levels of up to 290,000 ions/cm³, particularly in the winter months when visitor numbers are lower. Gamma radiation, toxic gases (CO, H₂S), and electromagnetic fields were consistently negligible or absent. The tunnel maintains a stable temperature (approximately 13–15°C) and high humidity (~85%) year-round. These findings position the Ravne Tunnel Complex as one of the most energetically distinct and environmentally controlled subterranean spaces studied to date. The data support the interpretation of Ravne as a safe, low-radiation, ion-rich environment potentially conducive to human physiological regeneration.
