The construction industry significantly contributes to material consumption, energy use, greenhouse gas emissions, and waste. To mitigate these impacts, circular economy principles—reduce, recycle, and reuse—are essential. While recycling is common for steel structures, it requires reprocessing energy. Reuse, however, further lowers environmental impacts by eliminating reprocessing. Although reuse is expanding in Europe, it remains underutilized in Italy. This paper explores reuse applications, specifically through a pilot study designing a seismic-resistant steel exoskeleton using components from dismantled Italian power pylons. The exoskeleton, rigidly attached to a reinforced concrete building case study, features a diagrid-like design. Its seismic performance was evaluated and compared to a similar exoskeleton made entirely of new steel members, with each solution assessed for sustainability.