5e SRD:Investigation Skill

Investigation. When you look around for clues and make deductions based on those clues, you make an  check. You might deduce the location of a hidden object, discern from the appearance of a wound what kind of weapon dealt it, or determine the weakest point in a tunnel that could cause it to collapse. Poring through ancient scrolls in search of a hidden fragment of knowledge might also call for an  check.