Because biological diversity is directly related to diversity of the physical environment, a clear picture of the physical setting of the Cordillera is crucial to understand its ecology and conservation. The physical setting of Monteverde and the Cordillera de Tilarán encompasses a wide range of environmental conditions. The size, position across the trade windflow, geology, erosional dissection, and hydrology of the Cordillera interact to produce extraordinary physical diversity that parallels its great biological diversity. A major difference between tropical montane and lowland regions is the way biological diversity is distributed across the landscape. Montane regions are usually less diverse at the scale of 0.01-0.1 km2 but are as rich in species as nearby lowland areas at scales of 10-100 km2. We have two goals in this chapter. First, we review what is known of the climate and weather, geology and geologic history, geomorphology, soils, and hydrology of Monteverde. Our account focuses on higher elevations in Monteverde and wetter areas on the Caribbean slope, with less attention to the drier environments on the lower Pacific slope. Second, we point out areas where our knowledge is incomplete and suggest promising lines of future research. Although the geology and geomorphology of Monteverde are moderately well known, our knowledge of the rates of many geomorphic processes, particularly erosion, is poor. We also lack information on soils and hydrology, particularly of wind-driven cloud and precipitation inputs, evapotranspiration, and stream outputs from forests and other land-use types in Monteverde. Quantitative information on how variability in the physical environment interacts with biotic processes at the population, community, and ecosystem levels is scant. Most of the climate and weather data were collected at 1450 m at the Pensiόn (1956-1971), at 1520 m at John Campbell's residence (1972 to present), and intermittently throughout or near the Monteverde Cloud Forest Preserve (MCFP; Lawton and Dryer 1980, Crump et al. 1992, Clark 1994, Bohlman et al. 1995, W. Calvert and A. Nelson, unpubl. data).