The installation of a centralised heating plant, just outside the Porta Sluderno, partially cut into a series of thick walls. The collapse of an arched-vault, constructed in gneiss stone slabs, was uncovered. The interior was filled up to the springing of the arch with colluvial sands. The vault sprang from two walls, each of a different thickness. The wall on a W-E axis is 1.10m wide and originates below the Porta Sluderno and its length was traced for 6m. The NE-SW wall, 2.50m thick, was traced for circa 3m. These walls have been interpreted as modern fortification against cannon fire. This hypothesis is supported by the walled artillary platforms, noted by Nothdurfter some years ago on either side of the gate, but which he never recorded.