Smellscape has increasingly attracted attentions across disciplines. However, little research provides a model to help understand the perceptual qualities of smellscapes. This paper, taking pleasantness as a perceptual quality dimension, aimed to explore indicators influencing people's pleasantness of smellscapes in a selected case. People's natural speaking language was used as resources to understand their perceptions. Grounded Theory was used as a methodological approach in this study in a selected case. Nineteen participants were recruited for smell walking with semi-structured interviews. Overall, nine indicators emerged from participants' descriptions which contribute to their smellscape pleasantness: cleanliness, preference, appropriateness, naturalness, freshness, familiarity, calmness, intensity and purity. Meanwhile, four types of pleasantness were found according to dominant indicators: preference dominated, healthiness dominated, memories and habituation dominated and context dominated. A perceptual model has been developed based on the indicators which can be used to classify smellscapes through their dominant perceptual features and evaluate smellscape qualities based on pleasantness.