Crown Guard Tower is a scout tower located in the Eastern Plaguelands. During the Scourge invasion of Lordaeron, Crown Guard Tower was destroyed and left in ruins. Later it became a battleground as it was one of the fallen towers that the Alliance and Horde fought over for in order to fortify themselves in Lordaeron. The Crown Guard Tower, along with all the other towers of the Eastern Plaguelands, have since been rebuilt by the Argent Crusade and is being used as an outpost for the region. Like the nearby Light's Hope Chapel, there are signs of life around the tower, and there is also a neutral flight master. 
To the right of Argus Highbeacon, there is a Argent Parachutes chest which applies a 5 second Parachute debuff. One can only presume that Blizzard understands the players' affinity for exiting a tower by jumping over the ledge.