## 1 Introduction  
Many important historical constructions are built in high seismicity areas and nowadays require interventions to improve their resilience. Considering the Italian historical heritage, several buildings that were originally designed to resist only gravity loads suffered serious damages during recent strong earthquakes, such as L'Aquila (2009) [1; 2; 3; 4; 5], Emilia-Romagna (2012) [6; 7], Amatrice (2016) [8; 9], and Ischia (2017) [10; 11]. Several researchers have proposed different techniques to improve the seismic behavior of historical buildings, for example, by the application of noninvasive and reversible systems [12; 13; 14; 15; 16; 17]. Removeable systems are often required to restore the original structure. Therefore, it is possible to improve the structure's seismic response by invasive modification of the original structure (solution 1) or by applying an auxiliary and reversible system that changes its dynamic response (solution 2). To improve the seismic behavior of slender masonry constructions, such as chimneys or towers, the use of steel reinforcements rings attached to the primary structure by steel rebars is commonly adopted (solution 1) [18]. In other cases, an inner spiral reinforcement is applied, as shown in Figure 1. For these slender constructions, structural improvements are necessary to overcome the dynamic effects caused by wind and/or seismic actions. Solution 2 is largely used in slender concrete [19; 20; 21] and steel [22; 23; 24] constructions. Possible examples of this solution are the chimney presented in [25] and the \"Arquata Scrivia chimney\" (Figure 2). In both cases, the used system was a tuned mass damper (TMD). TMDs have shown their effectiveness and robustness as vibration countermeasures tall and slender constructions, such as high-rise buildings and wind turbines. To design a TMD, different criteria should be considered, taking into account the possible distinct interactions of wind and earthquake with the structure. The application of the TMD on reinforced concrete and steel slender structures is deeply investigated [26; 27; 28; 29; 30]. However, there are no common examples of the application of a TMD on slender historical masonry construction. In the following, the criteria to design and optimize a TMD for a masonry slender structure are pointed out, considering, as an example, the case of a chimney part of a historical hydraulic plant. For this chimney, the owner requested a removable system to improve its seismic behavior. Furthermore, an appreciable combination of the TMD steel support structure with the existing masonry one was also needed. Figure 3 shows the first configuration with the TMD located at the top of the chimney. Another possible configuration of the TMD steel support structure is demonstrated in Figure 4 (second configuration). Figure 1: The use of steel reinforcements rings to improve the seismic behavior of slender masonry constructions (invasive modification of the original structure (solution 1). (**a**) Outer reinforcement, and (**b**) inner reinforcement. Figure 2: Arquata Scrivia chimney (AL, Italy). An example of applying an auxiliary and reversible system that changes its response under dynamic loads (solution 2). Figure 4: Proposed second configuration with the TMD located at the top of the chimney: (**a**) detail of the TMD support steel structure, and (**b**) a view of the damping devices. Figure 3: A 3D render of the real, tuned mass damper (TMD) design for a masonry slender structure proposed to the Italian Cultural Heritage. (**a**) The proposed first configuration with the TMD located near the top of the chimney, (**b**) steel TMD in detail, and (**c**) view of the historical hydraulic plant (Italy). In approaching a historical construction, two preliminary activities are required: (i) the geometric survey and (ii) the dynamic tests [31].