Modern technological advances have enabled digital automated methods to be applied for accurate and detailed documentation. Such techniques include image based modelling and terrestrial laser scanning. They can easily be adapted to perfectly suit the documentation needs for small and large objects. In this paper the digital geometric documentation of two medieval fortifications using such contemporary methods is briefly described. These are the western part of the Castle of Chios and an important part of the medieval Rhodes fortifications. The purpose of the geometric documentation for both cases was the restoration of these parts, hence detailed documentation was necessary. Conventional two-dimensional plans with digital orthophotographs were produced and from them conventional line drawings were required for the case of Chios castle. Both castle parts included cylindrical bastions, whose projection on two dimensional plans is obviously deformed. Such non-planar parts constitute a special challenge for the geometric documentation. To solve this problem the three-dimensional digital documentations of these parts were developed by using suitable development routines. Thorough presentation of all considerations for these developments are presented and the implementations are briefly described. The results of these developments are evaluated for their usefulness, accuracy, and efficiency as digital documentation products.