Complex sentence: Although most of the poem is supposed to take place in the late 20th century, there are sections of the poem that take place in the West Indies in the late 18th century (following ancestors of the characters Achille and Plunkett).
Split into simpler sentences: Although most of the poem is supposed to take place in the late 20th century, there are sections of the poem that take place in other time periods. For instance, there are chapters that take place in the West Indies in the late 18th century (following ancestors of the characters Achille and Plunkett).