Farthest Outpost is a song included in the Halo 3: Original Soundtrack. It plays during the beginning of the Halo 3 level The Ark.
The beginning of the song is based mainly on choir and strings. It is similar to the song In Amber Clad from Halo 2. At around 0:40, drums become the dominant instrument. Later on, the melody is taken over by strings again, playing the Arbiter's theme. After that, a section from the songs, Out of Shadow and the Halo 3 version of Perilous Journey, Make Them Pay will play.
The name of the song is most likely in reference to the Ark, which could be considered the "farthest outpost" of the Forerunners.
The song runs for 5:14.
At the beginning of the Halo 3 version of Perilous Journey, a heavy bass drum is audible in the background playing seven beats before resting and then repeating. This is another 7 reference.