#understructure__foundation__base__fundament__foot__groundwork__substructure  lowest support of a structure; "it was built on a base of solid rock"; "he stood at the foot of the tower"
  supertype:  support.supporting_structure  supporting structure that holds up or provides a foundation; "the statue stood on a marble support"
  part of:  physical_structure
  subtype:  bed.understructure  a foundation of earth or rock supporting a road or railroad track; "the track bed had washed away"
     subtype:  railroad_bed  a bed on which railroad track is laid
     subtype:  roadbed  a bed supporting a road
  subtype:  raft_foundation  a foundation (usually on soft ground) consisting of an extended layer of reinforced concrete

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