{
  "underground_features": {
    "cave_network": {
      "display_name": "Cave Network",
      "description": "Interconnected underground cavern system with multiple entrances",
      "formation_type": "limestone_dissolution",
      "budget_impact": 2
    },
    "underground_lake": {
      "display_name": "Underground Lake",
      "description": "Subterranean water body accessible through cave systems",
      "formation_type": "groundwater_accumulation",
      "budget_impact": 3
    },
    "crystal_cavern": {
      "display_name": "Crystal Cavern",
      "description": "Underground chamber with natural crystal formations",
      "formation_type": "mineral_crystallization",
      "budget_impact": 4
    },
    "bat_cave": {
      "display_name": "Bat Cave",
      "description": "Large cave system inhabited by bat colonies with guano deposits",
      "formation_type": "biological_cave",
      "budget_impact": 1
    },
    "underground_river": {
      "display_name": "Underground River",
      "description": "Subterranean watercourse flowing through cave systems",
      "formation_type": "groundwater_flow",
      "budget_impact": 2
    },
    "deep_cavern": {
      "display_name": "Deep Cavern",
      "description": "Extremely deep cave system reaching significant depths",
      "formation_type": "tectonic_cave",
      "budget_impact": 3
    }
  }
}