Systems, methods, and articles of manufacture provide for a mold system for molding structures (e.g., sand castles) from one or more various types of molding substances (e.g., sand, clay, snow). In one embodiment, a mold system comprises a split mold comprising at least two mold sections. In one embodiment, a modular mold system allows for different types of mold sections with corresponding joining elements to be joined together to create forms for molding various types of structures. In some embodiments, mold sections are configured to facilitate the breaking of a vacuum created when molding substances are packed into the mold system, thus making it easier to separate a mold from the formed structure.