In this paper a typical five-storied reinforced concrete plane frames with full isolation are analyzed, assuming two ground types namely rock and moderately soft soil. These two ground types are combined with fundamental vibration periods of 2, 3 and 4 seconds respectively in a high-risk seismic region with the overall isolation system. The isolation systems are made of in-parallel high-damping laminated-rubber bearings and supplemental viscous dampers. Real accelerograms at El Centro 1940 are considered and analysis is carried out with SAP 2000 Version 12 using time history analysis. It is concluded that a supplemental viscous damping at the base is appropriate for controlling the isolator displacement, so avoiding overly large isolators and it is found that displacement will reduce in both the soil conditions; also displacement is less for higher vibration period and a comparison is also made for a base isolated structure with and without supplemental damper.