The Monastery of Our Lady of Nazareth of Mocambo in Lisbon, usually known as Bernardas' Convent, was a Cistercian foundation (1653). In 1755 it was totally destroyed during earthquake and reconstructed later on by the Italian architect Giacomo Azzolini. After the extinction of the religious orders (1834) the Monastery had several uses. Nowadays, the monastic building serves a small condominium, a restaurant and the Puppet's Museum. As the building had to be preserved under historical regulation its unchanged exterior walls, since Azzolini's restoration, are made of solid masonry which dominates construction throughout the history. A well-known fact about this kind of buildings is their difficulty for temperature control that inevitably ends up using more energy to heat and cool, being experiencing a change in indoor climate due to different. Emphasis is placed in the thermal performance of these exterior walls from the view point of thermal comfort, following the ISO 7730 assumptions. The interior surfaces temperatures on heating season under climatic conditions of Lisbon are analysed. This paper aims to discuss, throughout a wide range of analysis, in which way the ideals and the realities of this historic building are divergent, but a factor of city growth and cultural development. (C) 2013 Elsevier B.V. All rights reserved.