In this paper, a case study of an unjustified reconstruction of a heritage masonry viaduct is presented. The damaged historic nineteenth century railway viaduct, located at the Dietla Street in Krakow, Poland, was subjected to deep expertise, aiming at adaptation of it to new railway standards. The Grzegórzecki Viaduct was protected by the law against demolishing by its location on the Polish register of monuments. A multi-disciplinary team was appointed, consisting of conservators, engineers and scientists, to protect it against a planned demolition for reconstruction during construction works. New safety railway standards and heritage conservation needed for the viaduct to be met in their upgrade, which has led to elaboration of evaluation experiments and adjusted reconstruction program. Deep multi-disciplinary investigation was carried out on the viaduct by the team, resulting in a compromise design, based on a multi-volume expert study, accepted by all authorities and stakeholders. The study followed the ISCARSAH guidelines, focusing on minimum intervention. The heritage status of the Grzegórzecki Viaduct was however removed by withdrawing it from the register of monuments, allowing thus for the viaduct demolition and further reconstruction of it in the initial form, as a reinforce concrete structure with masonry cladding. The Grzegórzecki Viaduct had not been saved. The historic bridge was lost for good: this despite the very many professionals who tried, without success, to show that alternative theoretical calculations may well prove that the bridge can be improved by strengthening methods, with a result where new capacity would exceed the required design load. This paper presents the special dilemmas posed by the maintenance of railways heritage as operational systems and the elaborated solutions for the monument protection. It also reflects on the personal experiences of the authors with this case study.