The beautiful national Route 48 "Toggenburger Höhenweg" connects Wildhaus and Wil SG. This FKT is done in either direction, starting at the train station in Wil SG and finishing in Wildhaus, or reverse.

You find a perfect description here: https://www.schweizmobil.ch/en/wanderland/routen/regionale-routen/route-048.html

Marble Mountain is a great peak among many situated in the heart of the Sangre de Cristo range. The peak is easy to identify as it flanks the south side of South Colony Creek Valley and Humboldt Peak. The route is a standard out and back, through old growth forest, alpine tundra and finally some talus toward the summit.