Digitally documenting complex heritage sites such as castles is a desirable yet difficult task with no established framework. Although 3D digitizing and modelling with laser scanners, Photogrammetry, and computer aided architectural design (CAAD) are maturing, each alone is inadequate to model an entire castle in details. We present a sequential approach that combines multiple techniques, each where best suited, to capture and model the fine geometric detail of castles. We provide new contributions in several areas: an effective workflow for castle 3D modelling, increasing the level of automation and the seamless integration of models created independently from different data sets. We tested the approach on various castles in Northern Italy and the results demonstrated that it is effective, accurate, and creates highly detailed models suitable for interactive visualization. It is also equally applicable to other types of large complex architectures.