Wind energy in cities has much-untapped potential for decentralized, renewable energy generation. The flow depends significantly on the local geography, so where a wind turbine is placed is one of the most critical factors. The present article assesses the effect of positioning a Darrieus (lift)-type Vertical-Axis Wind Turbine (VAWT) on the roof of the two model buildings replicating the urban wind flow conditions. Three-dimensional CFD simulations are performed to visualize the flow field and its effect on the turbine performance at six different streamwise positions (three on each model building). The Actuator Line Model (ALM), a combination of classical blade element theory and the Navier–Stokes-based flow model (with SST turbulence model), with its sub-models for the dynamic stall, end effects, added mass, and flow curvature, is invoked for numerical modeling of the VAWT. The turbine’s performance is assessed by comparing the flow characteristics with and without the turbine and by measuring the produced torque in terms of the power coefficient. The optimum performance is observed when the turbine is placed in the front (towards the windward side) on the roof of the first building due to the accelerated incoming flow over the flow detachment from the windward edge. It drops significantly as the turbine is shifted towards the leeward side of this building, leaving the turbine partially in the reverse flow conditions over the top of the first building. The reverse trend is observed for the downstream building.