Earthquakes pose a significant threat due to their unpredictability and destructive impact. Structural resilience against seismic forces has been extensively researched, with base isolation emerging as a widely adopted technique. This study evaluates the effectiveness of seismic isolation in buildings with varying heights and lateral dimensions. Using High Damping Rubber Bearings (HDRB), 27 structural models with different height-to-depth ratios and story counts (5 to 15) are analysed in SAP2000 through Response Spectrum Analysis. Key seismic parameters—including natural time period, base shear, storey displacement, and joint acceleration—are compared between base-isolated and fixed-base structures. The findings provide insights into the influence of building geometry on isolation efficiency, contributing to improved seismic design strategies.