The dominant characteristic of urban areas that differentiates from the rural areas is the intensive use of land. Proper analysis of the three-dimensionality of urban activities are not only critical for desired land use planning, but also crucial for prescribing such policies as zoning, building codes, set back requirements, sky exposure lines, floor-to area ratio. Conventional models treat urban activities as if they engage in only on surface of land. Thus the three-dimensionality of urban activities and the intensity of urban land uses are not explicitly reflected and represented in their results. I will present how three-dimensional urban land use activities can be modeled, logically and analytically. Use of land is intensified as building becomes taller with increased capital input but decreased land input. Analytically, three-dimensional input-output table will be presented to help with identifying intensive use of urban land, employing data obtained from US cities.