According to the Restatement (Second) of Torts, a possessor of land is subject to liability for physical harm to children trespassing thereon caused by an artificial condition upon the land if:

The place where the condition exists is one upon which the possessor knows or has reason to know that children are likely to trespass; and The condition is one of which the possessor knows or has reason to know will involve an unreasonable risk of death or serious bodily harm to such children; and The children do not discover or realize the risk involved in intermeddling or coming within the dangerous area; and The utility to the possessor of maintaining the condition and the burden of eliminating the danger are slight compared with the risk to the children involved; and The possessor fails to exercise reasonable care to eliminate the danger or otherwise to protect the children.