The region outside Stratholme and areas of King's Square and the Festival Lane in Stratholme itself are fully explorable, provided that you have not spoken to Arthas after using the [Arcane Disruptor] to locate the plagued grain.
The road towards Corin's Crossing and Tyr's Hand, which runs behind the inn you enter the instance through - blocked by fog blanking the screen.
The road to Hearthglen at the crossroads between the inn and Stratholme - blocked by the same fog, although the town of what is now Terrordale can be seen through use of Eagle Eye, or other abilities that let you see things from afar.
Elders' Square in Stratholme is blocked by a cart of grain, though you can still see the (perfectly intact) Alonsus Chapel on the other side.
The way to Crusaders' Square is blocked by gates that are only accessible by advancing through the instance.
The town hall is not accessible in the present-day Stratholme.
NPCs for Questing
There are two quest NPCs:
Chromie: In the cellar of the inn where you enter the instance, and on the road to Stratholme after uncovering the plagued grain.
Arthas<Prince of Lordaeron>: The main focus of the escort, who comes out from the main gate of Stratholme.
There are many NPCs with some connection to important events in WoW and the Warcraft universe as a whole seen here in the past. They are mostly affiliated with either the Scourge, the Alliance or the Argent Dawn. In addition, several of the NPCs are directly related to the Stratholme instance.