Cities are an ever evolving complex mix of people, nature, and built structures which all have to synergize to fulfill changing societal needs. In the past, we designed, built, and operated infrastructure systems as if they were wholly separate systems. But urban systems are like ecosystems: Infrastructures like species are highly interconnected with each other in complex ways. The water-energy nexus has been studied for some time now, but there are other interdependent systems that have not been well researched, such as the interdependencies of engineering infrastructure (e.g., transportation, buildings, etc), urban ecosystems (e.g., parks, green spaces, etc), and socio-economic conditions (e.g., real estate values, job market, business environment, tax revenue, etc). For cities to be sustainable and resilient over time even when faced with uncertain challenges, we need to understand the linkages between individual components within cities, similar to food chains in ecology. A conceptual model of urban infrastructure ecology is introduced. This model characterizes the interactions among and between urban system components, including engineering infrastructure, urban ecosystems, urban dwellers, socio-economic conditions, and global economic, social and environmental drivers (e.g., climate change or financial crises). The two presenters, representing the disciplines of engineering and geography, provide an example of how sustainable engineering modeling can be combined with spatially explicit resource and demographic mapping to further our understanding of urban sustainability.