Modernist architects often practiced in historical urban environment, where the need for new construction had risen after the devastation of World War II. Within the wave of urban modernization, major transformations in the historic centers of many European cities took place in the 1960s and 1970s. They resulted in the rise of the heritage preservation activities, reaching their peak in the 1990s. More than 120 European urban areas including the historic centers of many state capitals were recognized as UNESCO World Heritage sites in the early 21st century. MOMO architecture often is an important component of urban landscape and functionality there. Typologically diverse objects of high importance to the city inhabitants and guests were erected during the post-war period and the following years, however, their value is not always properly assessed, and maintenance of their original quality is threatened during the urban regeneration process - even at risk of conversion or demolition. Over the last decades, the UNESCO Historic Urban Landscape approach has been developed displaying significant evolution of ideas and practices for the conservation of urban heritage. Along with other tools for its management, public participation is highly recommended. It involves a wide range of stakeholders, enabling to better identify contemporary urban values, and allows city planners to respect urban landscape by setting goals for its preservation within the terms of sustainable development. Ambiguous viewpoints exist in the heritage preservation institutions and in society about the values of MOMO legacy to be preserved as the cultural heritage.