The very simplest shelters, tents, leave no traces. Because of this, what little we can say about very early construction is mostly conjecture and based on what we know about the way nomadic hunter-gatherers and herdsmen in remote areas build shelters today. The absence of metal tools placed limitations on the materials that could be worked, but it was still possible to build quite elaborate stone structures with ingenuity using dry stone walling techniques such as at Skara Brae in Scotland, Europe's most complete Neolithic village. The first mud bricks, formed with the hands rather than wooden moulds, belong to the Neolithic period and were found in Jericho. One of the largest structures of this period was the Neolithic long house. In all cases of timber framed and log structures in these very early cultures, only the very lowest parts of the walls and post holes are unearthed in archaeological excavations, making reconstruction of the upper parts of these buildings largely conjectural.