This longitudinal study analyses the evolving and divergent environmental impacts of rural and urban development pathways in Prayagraj District, Uttar Pradesh, over a critical two-decade period (2005-2025). Framed within India’s era of rapid economic growth and policy shifts, the research employs a comparative historical analysis to trace environmental change. Findings indicate that urban development, accelerating post-2005, transformed Prayagraj City into a hub of concentrated air and water pollution, waste generation, and urban heat island intensification. Conversely, rural areas experienced a deepening of agrarian crises, marked by severe groundwater depletion, deteriorating soil health, and the spread of non-point source pollution. The period witnessed the explosive growth of peri-urban zones as unplanned, hybrid landscapes where these pressures catastrophically converge. Utilising data from government reports, satellite imagery, and demographic trends, this paper argues that environmental governance failed to keep pace with development speed, leading to compounded vulnerabilities. The study concludes by projecting 2025 scenarios and advocating for a decadal lessons-learned approach, emphasising robust spatial planning, integrated water resource management, and a just transition for agrarian communities as essential for future resilience.