When developers join a software development project, they find themselves in a project landscape, and they must become familiar with the various landscape features. To better understand the nature of project landscapes and the integration process, with a view to improving the experience of both newcomers and the people responsible for orienting them, we performed a grounded theory study with 18 newcomers across 18 projects. We identified the main features that characterize a project landscape, together with key orientation aids and obstacles, and we theorize that there are three primary factors that impact the integration experience of newcomers: early experimentation, internalizing structures and cultures, and progress validation. Categories and Subject Descriptors D.2.9 [Software Engineering]: Management General Terms Human Factors