Land easements within dense urban neighborhoods of Seoul create a loose network of ambiguous zones between public and private. The various forms of informal appropriation of these "mini-lots" mostly serve selfish interests of individuals, but any imposition of order for public benefit faces complications due to rigid land ownership structure, or a lack of more detailed land use plans in Korea. This paper adapts a new definition of mini-lots, based on easement lines in lieu of a minimum size of buildable lots, to highlight the legal backgrounds for the formation of mini-lots. Based on this new definition, a visual survey of mini-lots in selected communities has revealed three types of mini-lots, and different informal uses were observed in each type. Possibilities for fostering certain uses for communal benefits, through a more collective use of mini-lots at a network of public spaces, may lead to a more fundamental resolution of the paradox of unbuildable land.