The Frozen Borderline – 1968–1970 is a two-disc compilation set of music by Nico, comprising The Marble Index (recorded in 1968, released in 1969) and Desertshore (recorded and released in 1970). The two CDs contain remastered versions of all the tracks from these albums, early/alternate versions of many songs, and two previously unknown tracks.
The last (fourteenth) track of the second CD contains a hidden fifteenth track after ten minutes of silence, which is an alternate version of "Frozen Warnings" (a song from The Marble Index) without the tremulousharmonium, leaving only Nico's vocals and the violins.
Tracks 1 to 8 are remastered versions of the songs from The Marble Index. Track 9 and 10 are two previously unknown songs. Track 11 and 12 are alternate versions of the two bonus tracks from the 1990 CD release of The Marble Index. Track 13 to 19 are early versions of the songs.