Youth’s bright palace
  Is overthrown,
With its diamond sceptre
  And golden throne;
  As a time-worn stone
Its turrets are humbled—
All hath crumbled
  But grief alone!Whither, O whither
  Have fled away
The dreams and hopes
  Of my early day?
  Ruin’d and grey
Are the towers I builded;
And the beams that gilded—
  Ah, where are they?Once this world
  Was fresh and bright,
With its golden noon
  And its starry night:
  Glad and light,
By mountain and river,
Have I bless’d the Giver
  With hush’d delight.Youth’s illusions
  One by one
Have pass’d like clouds
  That the sun look’d on.
  While morning shone,
How purple their fringes!
How ashy their tinges
  When that was gone!As fire-flies fade
  When the nights are damp—
As meteors are quench’d
  In a stagnant swamp—
  Thus Charlemagne’s camp
Where the Paladins rally,
And the Diamond valley,
  And the Wonderful Lamp,And all the wonders
  Of Ganges and Nile,
And Haroun’s rambles,
  And Crusoe’s isle,
  And Princes who smile
On the Genii’s daughters
’Neath the Orient waters
  Full many a mile,And all that the pen
  Of Fancy can write
Must vanish in manhood’s
  Misty light;
  Squire and Knight,
And damosel’s glances,
Sunny romances,
  So pure and bright!These have vanish’d,
  And what remains?
Life’s budding garlands
  Have turn’d to chains—
  Its beams and rains
Feed but docks and thistles,
And sorrow whistles
  O’er desert plains.

What It Means

This is a placeholder explanation generated by the low-overhead model. It interprets "Youth’s bright palace
  Is overthrown,
With its diamond sceptre
  And golden throne;
  As a time-worn stone
Its turrets are humbled—
All hath crumbled
  But grief alone!Whither, O whither
  Have fled away
The dreams and hopes
  Of my early day?
  Ruin’d and grey
Are the towers I builded;
And the beams that gilded—
  Ah, where are they?Once this world
  Was fresh and bright,
With its golden noon
  And its starry night:
  Glad and light,
By mountain and river,
Have I bless’d the Giver
  With hush’d delight.Youth’s illusions
  One by one
Have pass’d like clouds
  That the sun look’d on.
  While morning shone,
How purple their fringes!
How ashy their tinges
  When that was gone!As fire-flies fade
  When the nights are damp—
As meteors are quench’d
  In a stagnant swamp—
  Thus Charlemagne’s camp
Where the Paladins rally,
And the Diamond valley,
  And the Wonderful Lamp,And all the wonders
  Of Ganges and Nile,
And Haroun’s rambles,
  And Crusoe’s isle,
  And Princes who smile
On the Genii’s daughters
’Neath the Orient waters
  Full many a mile,And all that the pen
  Of Fancy can write
Must vanish in manhood’s
  Misty light;
  Squire and Knight,
And damosel’s glances,
Sunny romances,
  So pure and bright!These have vanish’d,
  And what remains?
Life’s budding garlands
  Have turn’d to chains—
  Its beams and rains
Feed but docks and thistles,
And sorrow whistles
  O’er desert plains." in the context of ""Lament" in Ballads, Poems, and Lyrics (1850), p. 126" to mean that wisdom is timeless.