This is joint work with L. Katzarkov, A. Noll, and P. Pandit in Vienna. A boundary point of the character variety gives rise to a spectral curve, and a harmonic map to a building. The differential of the harmonic map is the real part of the multivalued tuple of differentials defined over the spectral curve. Gaiotto-Moore-Neitzke have introduced the notion of "spectral network" associated with such a multivalued differential, determining the WKB approximation of the nonabelian Hodge or Riemann-Hilbert correspondences. We have tried to gain some insight into the relationship between the spectral network and the harmonic map to the building: basically, the spectral network lines are located where the curve intersects the codimension 1 faces of the building.