The Christchurch Women's Hospital, completed in March 2005, is the only base-isolated building in the South Island of New Zealand. The displacement capacity of the base-isolation system and the super-structure ductility capacity are designed to meet 2000-year return-period demands. Detailed structural evaluations after the 2010 Darfield Earthquake revealed damage only to sacrificial non-structural components at the seismic gaps. Because the structure is not instrumented, basic design information and ground motion records from nearby sites are used to estimate the responses to the main shock and a large after-shock. Results from this modelling effort are used to corroborate reports of structural response from staff present at the time of the main shock and aftershocks. Issues meriting further investigation are related to the local site conditions, soil-structure interaction, super-structure dynamics, interaction with the adjacent structures, and large-deformation effects.