Residential buildings dating back to the late 19th and early 20th century constitute an important element of the urban composition of many European cities, often determining their overall spatial expression. These buildings often require revitalization and sometimes also reconstruction or extension. Such activities make it possible to restore historical buildings to their former glory, but also to create new architecture, inscribed in the context of the place, yet bearing witness to modern times. Revitalization of historically and architecturally valuable but technically degraded residential buildings is one of the important elements of maintaining and sometimes rebuilding the image of modern cities and their sustainable development. However, revitalization activities require solving many problems of conservational nature, especially issues related to preserving the authenticity of the existing tissue, ways of reconstructing lost elements, and connecting historical architecture with contemporary architecture. Historic residential buildings of Sopot, a city located in Poland on the shores of the Baltic Sea, dating back to the late 19th and early 20th century, provide excellent research material for such considerations. In the article, the historical center of Sopot was examined, with particular emphasis on the historic Willa Halina from 1896 located there, which was revitalized (according to the design of the author of the article). Using such research methods as analysis of historical source material (iconography), observation (operationalization of preserved historical objects), comparative analysis of contemporary investments, and analysis of the revitalization design of “Willa Halina”, an attempt was made to present spatial and technical solutions leading to the desired effects in the revitalization process. This work aims to show (on the example of Willa Halina in Sopot) the author’s method of revitalizing valuable, historical residential buildings, complying with international conservation standards, including the Venice Charter, adopted in 1964 by the Second International Congress of Architects and Technicians of Historical Monuments. The paper also aims to present spatial and technical solutions leading to desired effects in the revitalization process, consistent with the idea of sustainable development.