Lanes, alleys, vacant lots, rooftops, surface parking lots.... The potential for infill is massive, and still largely untapped. Despite frequent concerns over high-rise density, we still do not use our urban spaces in an efficient manner, particularly at the scale of micro-infill. Interspatial Playground tackles the urban future, as we find ways to increase density, sustainability, and retrofit our cities to deal with climate change. Here, it aims to interrogate our attitudes towards interstitial spaces and how they might make denser urban living more pleasant. Lanes and alleys are a vital, untapped public spatial typology in the city that is largely overlooked because of underdevelopment and neglect. The time and resources it takes to approve a city or developer-funded improvement project for a laneway do not have the kind of agility needed to radically transform the public realm of the city in a meaningful, timely way. Interspatial Playground aims to use the space between buildings to animate these human-scaled spaces, encouraging people to not only walk through but engage with the structure through interactive seating and lighting components. This not only beautifies space, but makes it safer by introducing people and light, thereby making it useful to a broader demographic. The structure is modular and can be scaled up or down depending on site requirements. Elements can be pre-assembled and delivered on site.