From the World Dungeons page on the official World of Warcraft Community Site:
Once the jewel of northern Lordaeron, the city of Stratholme is where Prince Arthas turned against his mentor, Uther Lightbringer, and slaughtered hundreds of his own subjects who were believed to have contracted the dreaded plague of undeath. Arthas' downward spiral and ultimate surrender to the Lich King soon followed.
The broken, burning city came to be a haven for the undead Scourge, who gathered behind Stratholme's massive watchtowers and iron gates. In years past, both champions of the Light and zealots of the Scarlet Crusade ventured into Stratholme to battle these monstrosities - and, almost to a man, they failed. Now, these former champions of humanity stand resurrected, bolstering the Scourge further. If they are not sealed in their lair, the forces of undeath, led by the death knightLord Aurius Rivendare and the dreadlordBalnazzar, will soon boil forth to ravage Lordaeron once again.
Geography
Maps and subregions
Atlas map showing various shops that were in Stratholme.
Also known as Scarlet Side, FD Strat, Strat Scarlet, Strat Light, Scarlet Strath, Strath Live, Living Strat, Liveside, Hu(man) Strat, West Strat, SM Strat, the Stratholme Main Gate leads through the city's streets to the former Scarlet Bastion, wherein the former members of the Scarlet Crusade have been slain and raised into undeath by Balnazzar. As you progress through the cathedral, the Scourge forces will follow in your wake; upon killing Balnazzar, the entire building will become filled with the undead, and members of the Argent Crusade doing battle with them.
There are three bosses that can be summoned in the streets. The first is Fras Siabi in King's Square, who can be summoned be opening his box of tobacco. The second is Postmaster Malown. To fight him, you will first have to kill the Stratholme Courier in King's Square, and loot his mailbox keys. Opening all the mailboxes that the keys are for (spread throughout the instance) will spawn the Postmaster. The third is the Risen Hammersmith, who is spawned by looting the Blacksmith Plans in the Scarlet Bastion. These can either appear on the floor in the Hoard before Willey Hopebreaker, or on a bench next to Instructor Galford.