Simulation is widely seen as a space where procedural skills can be practiced in safety, free from the pressures and complexities of clinical care. Central to this approach is the notion of simplification, a stripping down of skills into their component parts. Yet the definition of simplicity is contestable, often determined by experts without reference to those they teach.The author uses the ha-ha, a hidden ditch around a large country house used by 18th-century English landscape gardeners to create an illusion that the house is surrounded by untamed nature, as a metaphor for the differing perspectives of expert and novice. The author proposes that this difference of perspective lies at the heart of many current problems with simulation and simulators.This article challenges the philosophy of simplification, arguing that procedural skills should not be divorced from their clinical context and that oversimplification of a complex process can interfere with deep understanding. The author draws on Meyer and Land's notions of threshold concepts and troublesome knowledge and on his own experience with patient-focused simulation to propose an alternative view of simulation, framing it as a safe space which can reflect the uncertainties of clinical practice and recreate the conditions of real-world learning. By reintroducing complexity and human unpredictability, simulation can provide a safe environment for assisting the transformational change that is essential to becoming a competent clinician.