Located at the intersections between the landscape, spectral memory, sound, and contemporary media technology, this thesis explores how spatialized soundscapes may serve as media to evoke the spectral memories of physical landscape? An audio walk “Inner Memory of the Post-Industry” was prepared to engage Carrie Furnace - a Pittsburgh historical landmark - as a proof of concept to understand the design of spatialized soundscape. Through the development of mixed reality audio walk, the experience design challenges the linear narrative structure that is commonly found in traditional audio walks (constrained, guided) and proposes a space- driven auditory wandering (open-ended, unguided). Mobile mixed reality is utilized to support sound localization and spatialization and this offers a more flexible and immersive way of exploring the landscape. The spectral memories of the landscape are realized through a virtual soundscape combing environment sound effects with oral history recordings. Taking advantage of the post-industrial landscape's distinctive aesthetics and it's spatial complexity as the stage for soundscape design, this thesis explores the juxtaposition between a multi-sensory visual and sonic experience and how it allows people to empathize with historical events to reinterpret the landscape identity. Building upon the proposed technical infrastructure for audio-based mixed reality, this thesis also introduces a workflow of visualizing and designing spatialized soundscapes.