Starting from Rifugio Berni, go down a small bridge to the meadows below and follow the signs for San Matteo.

The ascent to Cima Vallumbrina shares a stretch with that of Punta San Matteo, which is referred to.

You have two access options:

1) One crosses the meadows in the direction of the old abandoned hut and follows the trail that climbs to a hump, crosses it and descends into the glacier access valley (in which case one must first ascend and then descend a height difference of a hundred meters).

2) Or follow path 25 on the left that provides access to Pizzo Tresero, passing by the Ponte dell´Amicizia bridge and, without crossing the bridge, follow the little path or snowfields that go up the valley on the orographic left of the stream and lead to rejoin the little path that descends from the hump (in which case you avoid going up and then down the hump again).
Reaching the glacier access valley, climb the steep moraine slope on the right that leads to the moraine ridge where you meet a marked junction. Keeping to the right, continue to the Bivacco Battaglione Ortles bivouac, climbing to the Black Lake above, which you skirt to the left. Then, continuing to the left, following the cairns and yellow paint markers you cross a rocky area and by a channel of scree or snow you reach below a collar defended by war remnant reticulation still in good condition. Without reaching the Bivouac, just above to the right, continue left on a military mule track that first cuts across the mountainside, then climbs under the ridge to the summit, where there are important remains of fortifications.