In this thesis the appropriate aesthetic evaluation of designed landscapes is explored. The overarching research question for this thesis is: What is an appropriate appreciation of a designed landscape as a designed landscape? This overarching research question is split into sub-questions. The first sub-question is: What is the current theoretical basis for the aesthetic evaluation of designed landscapes and does it provide appropriate arguments for aesthetic evaluations? Two important points about the aesthetic evaluation of designed landscapes were found in the existing literature on environmental aesthetics and in critical evaluations of designed landscapes. Modern environmental aesthetics is focussed on natural environments as it has been shaped in response to early 20th century aesthetics, which was dominated by questions on art. The designed landscape phenomenologically related more to environments, but is ontologically closely related to artworks. Designed landscapes thus fall between two fields. The designed landscape has gone largely unacknowledged by philosophers and geographers. The lack of a specific theory for the appropriate appreciation of designed landscapes has made it easier for landscape architects and critics to miss out on the current insights of environmental aesthetics, leading to the inconsistent belief among landscape architects and landscape architecture critics that landscapes are scenic entities. Actual design criticism as offered in the Landscape Architecture Europe books is shown to be based on the inconsistent belief that aesthetic experiences of works of landscape architecture are mostly visual. To explore what an appropriate appreciation should be based in, first the ontology and phenomenology of one example, the post-war design for the landscape of Walcheren, is described and discussed. To explore its ontology, a literature research has revealed the design process and decisions. To explore the phenomenology, the descriptions of two walks on the island made by the author were analysed. The descriptions of ontology and phenomenology of Walcheren offer insights into the relevance for the aesthetic evaluation of this landscape of being designed and of the sensorial richness of this designed landscape. In both fields of ontology and phenomenology insights into aesthetic value go beyond the visible. The second and third part of the research answers the sub-questions about appropriate appreciation regarding respectively ontology and phenomenology of designed landscapes in general. The literature on topics adjacent to the field of landscape architecture, such as design and architecture aesthetics, was surveyed for aspects that might also be relevant for the aesthetic evaluation of landscape architecture. These aspects were then weighed according to a philosophical method of reasoning from first principles. Starting from a principle of appropriate appreciation, different cues were tested to see whether or not they have to be considered in such an appropriate appreciation. Following descriptions of the True Appreciation Principle (TAP) as provided by Lopes, cues were tested against the Appropriate Appreciation Principle for Designed Landscapes (AAP-DL): An appreciation of landscape L as a designed landscape is appropriate only as far as it does not depend counterfactually on any belief that is inconsistent with the truth about the nature of designed landscapes. Examples are provided where cues can influence one’s evaluation, and evaluation thus depends counterfactually on those taking those cues into account. If something might influence one’s evaluation one should consider it. The exploration has provided important cues for the aesthetic evaluation of designed landscapes. The findings are the base of an evaluative framework that takes into account the ontology and phenomenology of designed landscapes in order to evaluate designed landscapes according the AAP-DL. A discussion is provided on the importance of such an appropriate appreciation for different audiences.