Virtual time travel transforming the existing remains of a heritage site to its original condition has value for education and cultural understanding. However, digitally reconstructing objects which no longer exist is a challenge. Interaction and navigation within virtual 4D worlds (adding time to 3D worlds) is also problematic due to imprecise understanding of the time dimension. In this project we developed an approach to 3D modeling of sites that have undergone changes over the years. The method creates independent models from different types of data, such as frescoes, paintings, drawings, old photos, historic documents, and digitized remains. The models are assembled and integrated for a 4D interactive presentation. Several research issues have been addressed: (1) Modeling from frescoes and drawings with incorrect perspective, (2) modeling from paintings and old photos including fine geometric details from shading (3) coloring models from old photos and drawings to match existing elements, (4) creation of models by seamless and accurate integration of data obtained from independent sources, and (5) the creation of intuitive interactive presentations that link the models with other multimedia components and information related to the history of the site. We will describe contributions to these issues, including our own advanced model viewer [Dem ], and apply them to modeling heritage sites such as Venice which appeared in paintings by Canaletto, Bernardo Bellotto, and Francesco Guardi, and many 19th century photos. Canalettos paintings have been used to measure the subsidence of Venice [Camuffo and Sturaro 2003].