Wind turbine wakes are complex, turbulent structures characterized by reduced velocity, because of the extraction of energy and momentum from the wind by the turbine, and increased turbulence intensity, due mainly to the swirling vortices created by the pressure difference at the blades' tips. Wake losses, occurring when turbine wakes reduce the wind speed downstream, are a significant challenge in wind farm performance. Even after layout optimization, these losses can decrease energy production by 10-20% and significantly impact the levelized cost of energy of wind farms. Several techniques are being investigated to mitigate wake losses and improve the performance of existing wind farms. One example is wake steering by wind turbine yaw control, which deflect wakes away from downstream turbines by changing the yaw angle of the upstream turbine. Passive methods, such as wake redirection via external vanes \cite{Nouri2022}, have also been studied. In this work, we investigate another passive method to accelerate wake recovery, which is the placement of a square obstacle on the ground, downstream of the wind turbine. We perform large eddy simulations of the flow through a 5 MW wind turbine, modelled with actuator lines and operating in optimal tip speed ratio in flat terrain, and measure the wake characteristics without and with an obstacle downstream, varying the size and position of the obstacle. The simulations are performed for neutral atmospheric boundary layer, for a single wind speed and ground surface roughness.