It is a privilege to write the preface for a book which materializes the outcome of a research programme like the PDL/BBO, which took five years to set up and lasted for ten years. It reminds us of the ‘cloud of nostalgia’ mentioned by one of the authors, Koos Bosma, when he is looking back to the Belvedere policy and refers to heritage perception and experience. The PDL/BBO programme and its unsuccessful pre-proposal submitted in February 1995 are a monument to the perception and experience of doing landscape and heritage research. The preface to this book also means closing an enterprise that has been made possible by the high ambitions of a few, the vision of some more and by the joint efforts of many. And by the pivotal role of Peter Schroder, former official of the Ministry of Education, Culture and Science in 1998!

This book is about the cultural-historical landscape and understanding and managing its heritage. On the European level the topicality of this theme is expressed by the European Landscape Convention and by the increasing need for integrative research. Against this general background, however, the researchers contributing to this book focus on a particular type of the cultural-historical landscape and a specific problem related to it: the (almost) invisible archaeological-historical landscapes and how to know them in order to manage them in a sustainable way. The (almost) hidden landscapes represent the majority of the cultural landscape, while what we see is only the tip of the iceberg. The hidden landscape is like the universe the astronomer is exploring, it is a resource of knowledge about past developments of people, landscape and environment with an unknown dimension and containing unimaginable information if we are prepared to look for what is hidden.

Triggered by the fascination for the unknown and by the value of landscape for present and future life, the researchers present an innovative integrative approach linking knowledge and action to deal with the particularities of the hidden landscapes. Although focused upon this specific issue, the approach is of basic value for the exploration of cultural landscapes in general and the management of its heritage in the context of the transformation of our actual environment and society.