Model tests with a Gravity-Based Structure (GBS) platform in extreme waves are presented. First, the background for the experiments is given, based on the analysis of a possible late life production scenario in the Statfjord field. The statistical approach applied in the specification of the wave conditions, and the laboratory reproduction is then described. This is focused on the generation of a statistical ensemble of 50 extreme crests sampled from random wave realisations. The model test set-up and instrumentation is described. Finally, results on deck impact loads and nonlinear wave amplification effects are presented and discussed.