This paper explores the feasibility of energy harvesting in the historic built environment. The ultimate goal of the research is to invent self-powered digital health monitoring system for the protection of heritage structures. This paper tackles two tasks. First, a vibration measurement test is carried out on a historical building standing over a metro line. Vibrations were measured in the sub and super structures. Second, taking advantage of the vibrations obtained from the measurement test, an energy harvesting test is performed. A piezoelectric actuator is evaluated, using a vibration testing machine. Barcelona city in Spain was chosen as the case study considering its rich heritage resources and busy metro network. According to the measured metro vibrations, a health monitoring test may be appropriate to observe the long-term impacts of the metro vibrations on historical buildings. On the other hand, the test showed these vibrations provided sufficient energy for energy harvesting. This paper presents results obtained in a preliminary phase of the research to explore the potential of energy harvesting for the health monitoring test of historical structures.