Why Does HtmlActionLink Always Prefix The Urls With The "Blog"

i have defined the following Routes:

routes.MapRoute("Blog",
"Blog/{controller}/{action}",
new { controller = "Test", action = "Index" });
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);

When i call http://localhost/ all Links are wrong and go to the Blog: @Html.ActionLink("About", "About", "Home") creates the following URL: localhost/Blog/About but it should create localhost/About. Why does HtmlActionLink always prefix the urls with the "Blog"?