“Descend into the earth with me.” We are about to explore the Grotta di San Lorenzo. This cave is also known as Jama na Jezeru. It is a hidden gem in Trieste.
The Grotta di San Lorenzo was discovered in 1920 by Marcello Marovelli. He considered it one of the most beautiful caves in the area. Let’s delve into its history and unique features.
The main entrance to Grotta di San Lorenzo is quite narrow. It opens in a rocky outcrop near Val Rosandra. Specifically, it is 500 meters south of the small church of San Lorenzo. The entrance sits at 405 meters above sea level. Getting inside takes some effort.
Once inside the Grotta di San Lorenzo, you will notice the access shaft. It is unusually inclined. This leads to a nearly circular cavern. From here, four branches extend. Once, all were adorned with stunning columns and stalagmites.
The most extended branch ends in an inter-layer fissure. This gap is too small to pass through. However, about 20 meters before this fissure, a side branch leads to a small pool of water. Beyond this pool, an impassable narrow passage suggests there are more chambers.
Grotta di San Lorenzo is very close to both the Val Rosandra cliff face and the Grotta Guido. In fact, a smoke test was conducted to see if Grotta di San Lorenzo and Grotta Guido connected. Smoke released in Grotta di San Lorenzo emerged in Grotta Guido. This suggests a connection, maybe a small impassable shaft.
The cave’s planimetric development stretches 185 meters. Its spatial development reaches 249 meters. The Grotta di San Lorenzo descends to a depth of 47 meters. The bottom sits at an elevation of 358 meters.
Marcello Maroevich described the cave vividly. A very narrow hole opens among the rocky blocks. It sits just six meters from the edge of Val Rosandra. The access shaft is about 29 meters deep. Its walls are uneven. They are covered with many crystalline formations.
Beyond the shaft, beautiful galleries and small caverns await. These are rich in crystals and white draperies. An opening supported by a large column leads to the first gallery. This gallery is entirely covered in crystalline concretions. White stalagmites decorate the space. The vault gradually lowers to a dense group of white columns.
Crawling through these columns, one reaches a short inclined plane. This plane leads to a second small cavern. This too is encrusted with shining formations. With a ladder, one can descend beyond a fissure. This leads to other niches.
In one of these niches, a short stretch of rock separates you from Val Rosandra’s wall. The colors here are extraordinary. Bands of red clay alternate with white stripes of chalky mud. White stalactites and columns intertwine with the red roots of external plants. This gallery marks the cave’s greatest depth at 48 meters.
Returning to the detrital cone, the second gallery lies to the right. Descending an inclined plane of debris, a small niche appears. Here, very white formations reflect in the clear water of a small basin. The 15-meter-long gallery has a group of stalagmites in the middle. These rise above blocks fallen from the vault.
Below the entrance to the third gallery, a small cavern is full of stalactites. To pass into the gallery, one must cross a forest of columns. Here, white walls are transparent and shining. The passage narrows. The walls resemble marble. Elegant white columns rise from the ground. They reflect in pools of water framed by crystalline roses.
Continuing on, various formations lead to the final cavern. Here, shining red concretions are covered in white corals. A small hole marks an impassable continuation. The fourth gallery is reached after retracing the 27 meters of the third gallery. This gallery is the widest and largest. The vault rises to a height of 11 meters. A covered inclined plane climbs with stubby stalagmites. White straws descend from the reddish walls covered in a clayey layer.
Grotta di San Lorenzo presents a variety of structures and formations. The cave runs parallel to the external wall for 20 meters. The underlying galleries are a few meters below ground level. This makes it a unique speleological site.
In 1991, the GTS completed a full survey of Grotta di San Lorenzo. This cave offers a glimpse into the hidden beauty beneath our feet. Remember its discoverer Marcello Marovelli. Remember the explorers who mapped its depths. As we leave, carry with you the wonder of this subterranean realm.