Consider this a portal. This cave entrance before you is the Jama also known as Antro di Bagnoli. It is a window into the depths of the Carso Triestino.
This is no ordinary cave. The Antro di Bagnoli is the most important spring in the Trieste area. Alongside the Antro delle Ninfe it is the only penetrable resurgence in the Val Rosandra.
During periods of little rain water does not flow from the entrance. Some pools further down the valley remain active. Heavy rainfall causes a significant flow of water from the cave. The flow can be impressive.
The cave is a single almost vertical fissure. It drains water from the Carso plateau. This includes likely connections to the sinkholes of Becca and Occisla. Its origin is unique. The limestone layers are arranged almost vertically. This created a drainage path for water.
Romans recognized the copious spring in 178 BC. They channeled its water with Fonte Oppia and Sorgenti di Bagnoli into a long conduit. This led to the new city. No traces of this first usage remain today. A tunnel near the wash house was thought to be Roman. It dates back to 1804.
That year marked the beginning of water research. Trieste needed water. Municipal wells and local springs were insufficient. The population was rapidly increasing.
Governor Conte Lovacz initiated a project. Miners from Idria were to dig a tunnel. It would connect the Antro to the spring below. This would combine both outflows into one channel. The work was abandoned after twenty meters due to negative results.
The Bagnoli spring was repeatedly considered. It was for various aqueduct projects for Trieste. Analyses showed its water was second best after Dolina’s. Its flow was too low. The average was 1200 cubic meters. The maximum was 23400 cubic meters. Other solutions were preferred.
Scholars identified the source of Bagnoli’s water. It came from streams swallowed by caves. These caves were on the Altopiano di S. Maria di Occisla. Professor Timeus proved this in 1908. He released dyes into the water. Fluorescein and fuchsine reappeared after 60 days. This happened after a heavy rain.
The experiment revealed something interesting. The Antro’s waters are independent of the nearby spring’s waters. The spring’s waters come from the Voragine di Occisla and Grotta della Cascata. The spring water is clearer and cooler at 12 degrees Celsius. The Antro’s water is often stagnant.
A less scientific test also convinced locals. Cavoli from Becca appeared from the Antro. These cavoli were swept away by a flood from Becca’s fields.
Today the cave is no longer the town’s wealth. Boegan wrote this in 1900. Recent renovations show the spring’s ancient importance is not forgotten.
The Antro di Bagnoli is accessible for only a few meters. The narrow rocky step alongside the water ends. It ends at a progressively narrowing fissure.
In 1960 divers from the Commissione Grotte Eugenio Boegan explored the underwater tunnel. The tunnel continues straight and widens downwards. The maximum depth reached was 28 meters. Murky water hindered further exploration.
Exploration continued in 1965. The Circolo Idrologico Speleologico Friulano took over. Divers from the Commissione Grotte made many underwater surveys. They ascended the submerged tunnel for about forty meters. They found no open-air chambers.
In 1976 a descending gallery was found. It was heading northeast. The bottom of clay and debris sloped at 45 degrees. It went down to 46 meters. The dive was stopped for safety reasons. Water came from above. It came through passages impassable by humans. Poor visibility and large chambers made further exploration difficult.
Explorations in 1991-1992 covered about 300 meters of new submerged tunnels. The maximum depth reached was 51 meters. The minimum was 32 meters. The average was 38-40 meters. Dives lasted three to four and a half hours. Poor visibility prevented mapping.
In 2000 the Antro di Bagnoli was the site of a diving campaign. The Slovenian speleodiver Tomo Vrhovec explored over 200 meters. On February 11 an unexpected accident occurred. Tomo did not resurface. His body was found at fifty meters depth.
Years later Andrea Moro found a tablet with notes and measurements. This tablet contained survey data. Tomo Vrhovec collected it before the accident. These measurements allowed a new survey of the cave to be drawn.
Investigations show the Antro di Bagnoli is the overflow spring. It overflows from the Sorgente del Lavatoio. The spring in the square is independent. It is independent of both the Antro and the Sorgente del Lavatoio. Dye tests indicate the Sorgente delle Ninfe and Sorgente Clincica are partly fed by the lake. This lake is under the Cascata.
So as you stand here remember the Antro di Bagnoli. It is more than just a cave. It is a source of life. It is a place of mystery. It is a challenge to explorers.