Old Indian cities are often less accessible due to temporal restrictions and ever‐rising pedestrian volume. In this research, the accessibility of the footpath‐level walkability condition of old core cities has been assessed through Architectural Planning Research, considering 32 footpath stretches in Central Kolkata, India, as a case. The research has considered 3 data sets, (a) 257 experts' opinions about universal mobility, (b) 18 variables for assessing accessibility conditions, and (c) peak hour pedestrian volume. IBM® SPSS® Statistics 26.0 version has been used to validate the findings of the research. It was found that mixed‐use buildings demarcate the edge of the footpaths in old cities. 50.6% of Indian experts have prioritized the “dimension of the footpath” while assessing universal mobility for pedestrians in the old cities of India. The average accessibility percentage for the entire surveyed stretch is negative which highlights the poor accessibility of the stretch. Pearson's correlation between footpath width and infrastructure score of 0.535 signifies the width of a footpath plays a significant role in determining the level of footpath infrastructure. Thus, the findings of this research can be used while preparing accessibility development plans for the study area and other areas of a similar genre. In this research, the accessibility of the footpath‐level walkability condition of old core cities has been assessed through Architectural Planning Research, considering Central Kolkata, India, as a case. The findings of this research prove the relationship between footpath width and the footpath infrastructure.