Those look like the old asphalt pavers that were used on Monument Ave.

As for trolly tracks, I live on China St on a trolly line. The water main is under the tracks. Any time someone requests lead line removal they have to cut out the trolly rails. I have a few segments saved! :)

As I have been told, the small almost square stones used in the bottom were ballast from ships. I don't know if this is true. But interesting