A heightened standard of care may apply as to artificial conditions on D's land.
1) The artificial condition is a foreseeable risk of unreasonable danger to trespassing children (if D knows or reasonably should know of the existence and nature of the artificial condition. D has no duty to inspect to discover the artificial conditions)
2) it is foreseeable that children are likely to trespass where the artificial condition is located. If D has no reason to anticipate children trespassing then no heightened standard of care. Past trespasses, proximity to children areas, accessibility to artificial condition. "attractive nuisance doctrine"
3) the child trespasser is unaware of the risk - age, immaturity, did not discover the condition or did not appreciate the danger. If able to understand risk, danger, aware of condition, avoid risk, no higher duty
4) the risk of danger of the artificial condition outweighs its utility - the utility of maintaining the dangerous artificial condition must be "slight" compared to the risk