Abstract: The modular base for a playing structure, such as a toy building set, includes a first planar member, or tile base, having attachment fittings on its bottom for removable attachment to a substructure, such as a lattice. The top of the first planar member has attachment fittings thereon. Preferably, each of the attachment fittings on the top of the first planar member are aligned with one of the attachment fittings on the bottom to form a common opening through the first planar member. The modular base also includes a second planar member, or tile, having attachment fittings on its bottom. The attachment fittings are preferably protrusions that are most preferably clover leaf in shape and have an interference fit with the attachment fittings on the top of the first planar member that are most preferably square openings.

Abstract: A modular building for a toy building set includes a planar member, or foundation, having raised ribs on its top and a wall member having a wall portion and a base portion. The wall portion of the wall member is substantially orthogonal to the base portion of the wall member. The base portion of the wall member has a cleft therein sized to receive one of the ribs of the foundation to removably attach the wall member to the foundations. A substantially planar coupler connects at least two or more of the foundation. The coupler has at least two clefts therein. The clefts are sized to receive the ribs on each of the two foundations for removable attachment of the foundation to the coupler.

Abstract: The modular lattice substructure for a playing structure, such as a toy building set, includes a planar frame having a plurality of exterior corners and a column having a height greater than the height of the frame. The column includes a lower portion and one of the lower portion of the column and a corner of the frame have a receptive connector thereon for removable attachment to a protrusion connector on the other of the lower portion of the column and a corner of the frame. In this manner, a single frame can be attached to a plurality of columns, and a single column can be attached to a plurality of frames in order to form a modular lattice substructure for a playing structure.

Abstract: The modular lattice substructure for a playing structure, such as a toy building set, includes elongate beams, elongate joists, and columns having a height greater than the height of the elongate beams and joists. The sides of the columns have a protrusion connector removably attachable to a slot connector in the ends of the elongate beams and the ends of the elongate joists.

Abstract: The modular terrain for a playing structure, such as a toy building set, includes a plurality of terrain pieces. Some of the terrain pieces have a flat exterior edge. The flat exterior edge is only matable with a flat exterior edge on another of the terrain pieces. The flat exterior edge has spaced longitudinal end points. The flat exterior edge has no change in height between the spaced longitudinal end points. The distance between the spaced longitudinal end points of the flat exterior edge is one of Y, .sqroot.2Y and 2.sqroot.2Y. Some of the terrain pieces have a hill exterior edge. The hill exterior edge is only matable with a hill exterior edge on another of the terrain pieces. The hill exterior edge has spaced longitudinal end points. The hill exterior edge has a change in height between the spaced longitudinal end points of X. The distance between the spaced longitudinal end points of the hill exterior edge is Y. Some of the terrain pieces have a slope exterior edge.