The 1998 expedition to Slovenia marked the fifth consecutive year of exploration on the Migovec Plateau in the Julian Alps, Slovenia. Building on previous work, the team extended the known cave system by an additional 2.3km, bringing the total surveyed length to 9.46km, and increasing the depth to –970m, making it the third‑longest and fifth‑deepest cave in Slovenia. The system’s complexity at depth—unmatched elsewhere in the region—had attracted increasing national and international attention, including presentations at European and British caving conferences and coverage in specialist publications.
The expedition operated from three logistics hubs: a base camp (900m), an advanced plateau camp (1,800m), and an underground camp, Hotel Tolminka, situated at –620m. Improvements to the subterranean camp, such as newly crafted Polartec fleece liners, significantly enhanced comfort and enabled efficient three‑day deep‑exploration trips. Despite a major earthquake earlier in the year, the cave structure showed no detectable damage.
Exploration focused on both low‑level and high‑level leads. Key low‑level discoveries included major new passage development in Paradox Passage, leading to a sump at –967m (Pencil Sump), and extensive new areas such as Elephant Chamber, Waterloo, Wonderstuff, and Earthquake Way (–937m). Additional Slovenian winter exploration extended the wet route to Water Hope, reaching the cave’s current deepest point at –970m. High‑level exploration targeted leads off Exhibition Road and Level 2, including the Britannic and Titanic pitches and new connections such as Poltergeist and Waffles, though several routes ended in tight rifts.
Scientific work continued with geological mapping, hydrological dye tracing, and cataloguing surface entrances. While dye tracing produced no conclusive results, geological data strengthened understanding of fault‑controlled passage development. Innovations such as a steel‑cable traverse and improved solar‑charging systems supported safer and more effective exploration.