Satellite imagery is a useful resource for tracing building footprints if no other data exists. (Note that 3D models of many cities around the world are available from a variety of sources, including Open Street Maps, Google’s 3D Tiles and other research institutions).
If you are unable to access 3D building data for an area and time period of interest, you can use the satellite imagery to trace the building shape and rely on other data sources to recreate building heights.
Google Earth gives access to historical satellite data and has a suite of useful research tools, including an easy way to map and measure spatial data.
This 2022 article from Sky Watch describes a number of services that provide free access to satellite data.