What is the grammatical role of the "lay" in the following sentence? It seems like a verb. But why it is not used like a third person form (lays) or "lay" is the past form of it?
First, attention may be given to the doctrine of geographic causation. It stresses the decisive importance of the location on Moscow for the later expansion of the Muscovite state (the medieval state centered in Moscow) and includes several lines of argument. Moscow lay as a crossing of three roads. The most important was the way from the historically crucial city of Kiev and the declining south to the growing northeast.