This depends on the city, but absolutely nothing would be a reasonable option.

In the case of a major city, scattered blocks of dressed stone. Not a lot else.

Pretty much everything in that time period was made of natural materials, after 1500 years it would be gone. Some larger metal objects might leave traces, say an anvil might appear as a rusted lump of metal. Dressed stone would be weathered but might be recognisable as having once been part of a building but there's a high chance that it would all be buried under a couple of feet at least of soil. Deciduous forest is probably the worst place for this as it lays down new soil fairly quickly. 1500 years is also enough generations of trees to have demolished the buildings.

This depends on the city, but absolutely nothing visible would be a reasonable option.

In the case of a major city, scattered blocks of dressed stone. Not a lot else.

Pretty much everything in that time period was made of natural materials, after 1500 years it would be gone. Some larger metal objects might leave traces, say an anvil might appear as a rusted lump of metal. Dressed stone would be weathered but might be recognisable as having once been part of a building but there's a high chance that it would all be buried under a couple of feet at least of soil. Deciduous forest is probably the worst place for this as it lays down new soil fairly quickly. 1500 years is also enough generations of trees to have demolished the buildings.