From Connolly and Hodge, The Ancient City
Here is the Panathenaic procession passing through the Propylaea ('Gateway'). In the distance (top center), you can see smoke rising from the great altar of Athena. The Temple of Athena Nikê ('Athena Victory') is located on top of the bastion to the right of the approach ramp adjacent to the Propylaea to the right. For how it looks today, see photo below.
Thanks to Kevin T. Glowacki and Nancy L. Klein