The Horseguards - This large edifice consists of a center and two wings.  It is called the Horse-guards, because the troops called by that name, mount guard there; two of them, compleatly armed and on horseback, are constantly on duty as centinels, under two handsome pavilions detached from the building, which were to shelter them from the weather.  In the centre is a vaulted passage which leads into St. James’s Park.