The present study analyzes the visual phenomena experienced while walking through each of the following three underground spaces through the perspective of ecological geometry: the Ekimae-dori underground walkway, Crysta Nagahori shopping arcade, and Tenjin underground shopping mall. Through this analysis, the study aims to clarify an aspect of the relationship between the quality of the user experience provided by each space and the physical characteristics that construct these qualities.

 Prior to the present study, to investigate the visual perception of the above-ground and underground spaces of Sapporo Ekimae-dori, a comparative analysis was performed on the visual occluding phenomena experienced while walking through these above-ground and underground spaces. Based on these previous studies, the current study positions itself as an embryonic study that attempts to describe visual experiences realistically using an ecological approach, with the ultimate aim of exploring the design possibilities inherent in the fact that underground spaces provide long-distance, indoor spaces specific to pedestrians.

 The underground spaces selected for investigation were chosen based on the following three conditions: (a) the total length and shape of the space are similar to the Ekimae-dori underground walkway, (b) the ground and underground routes run in parallel and the underground space has facilities for introducing light from above ground, and (c) the space not only functions as a commercial facility but also has the characteristics of a passage space. The visual phenomena in each underground space were converted into data by filming videos with a wearable camera while walking along pre-determined routes. While filming the videos, the horizontal and vertical angles of the camera were set at ~120° and ~70°, respectively and the height of the center of the lens was set at 150 cm from the ground to mimic the human field of view.

 In the analysis, the variations in the edges and textures constituting the series of visual spatial experiences obtained in each space were interpreted quantitatively in terms of pixels. Then, descriptions were written for scenes in which these variations had resemblance; in other words, scenes that provided experiences of similar quality. A scene was defined as a visual experience of 10 s, corresponding to 150 frames of continuous images taken at 1/15 s intervals. The degrees of similarity of the obtained scenes were visualized, and the characteristics of the visual experiences in each underground space were clarified.

 (1) The visual experience in the Ekimae-dori underground walkway constituted the following three elements: “building, ” “passersby, ” and “appearance of stores, ” and was of similar quality to the visual experience arising from the “building” element in the Crysta Nagahori shopping arcade. Thus, the “building” element in the Ekimae-dori underground walkway was simply compared to that in the Crysta Nagahori shopping arcade.

 (2) Unlike the Ekimae-dori underground walkway, the Crysta Nagahori shopping arcade and the Tenjin underground shopping mall are similar such that both sides of each walkway are lined with stores, and the widths of the walkway in a section of each route are similar. Thus, the visual experiences formed are of similar quality.

 (3) The visual experience in the Tenjin underground shopping mall, characterized by a narrow, dimly-lit, tunnel-like walkway, is of similar quality to that in the wide and thoroughly-lit Ekimae-dori underground walkway. From this fact, it is inferred that the walls of the Tenjin underground shopping mall, which are lined with shutters, and the walls and columns that line the Ekimae-dori underground walkway create visual experiences of similar quality.