Thanks to Marco Boglione for the information about the reason for the collapse and for identifying some storage areas.

Characteristics

Battery B3 or the  615th Battery G.a.F. (Guardia alla Frontiera or Frontier Guards - a special corps of the Italian Royal Army created in 1934 and dedicated to the garrison of the works of the Alpine Wall) is an underground works constructed between 1933 and 1935 in the rocky mountain walls below the Plateau of the Fontanette ⁽¹⁾.

The works was manned by 90 soldiers and consists of:

• two separate entrances;
• four artillery posts in metal casemates with field of fire toward the south-west side of the lake;
• an underground observation post with an armored plate;
• an emergency exit;
• two underground living quarters;
• various storage areas.

Weaponry

• 4  75/27 pieces, model 06.

Description

Battery B3 is laid out on two underground levels and is supplemented by some external storage areas located near the lower entrance.

The upper entrance leads to a long series of steps which descend to a large underground living quarters from which two other sets of stairs lead to the level below

The corridor from the lower entrance passes a couple of storage alcoves and then turns to the left and follows a line parallel to the side of the mountain.
In this section you find the lower living quarters, the branches which lead to the four casemates, and various storage areas.

After you pass the branch to the last casemate, the corridor continues along a curved set of stairs which descend with large steps to the observation post.

A little after the end of the steps you find the trapdoor of the emergency exit whose shaft opens to the outside near the embrasure of the observation post.

Conditions of the works

At the beginning of 1945 Battery B3 was sabotaged by the retreating Germans who caused the collapse of the arch between the second and third casemates and some related damage to the surrounding areas which seriously compromise the stability of the entire construction.

The considerably damaged zones are found:

• in the quarters between the first and second  casemates;
• in the quarters between the third and the fourth casemates;
• in the last part of the upper living quarters and in the steps which descend to the corridor below;
• in the corridor which descends to the observation post.

The collapse of the arch of the quarters between the second and third casemates cause the crater visible above ground and which is located above the upper entrance.

After the war metal grills were used to bar the entrances and the embrasures of the metal casemates.

All portable metal materials, such as the moving parts of the doors, the covers of the trapdoor of the emergency exit, and tubes of the ventilation plant have been removed..
The only exceptions are the external door of the emergency exit, a storage container attached from the ceiling of the alcove of the power supply group, and some sections of air tubes imbedded in the walls.