The City was utterly destroyed in 587 BC by the Chaldeans. The Septuagint, the earliest Greek translation of the Hebrew Scriptures, translated by 70 scholars in the 200 BC. This translation begins: “And it came to pass after Israel had been taken away into captivity and Jerusalem had been laid waste that Jeremiah sat weeping and lamented this lamentation over Jerusalem and said.”
The Septuagint was used by Greek speaking Jews until the Christians adopted it. The Jews, around 70AD, refused to use this translation.
Jerusalem was totally destroyed. The modern reader may wonder at the extremes of sorrow expressed in the book and may be puzzled that the Jews should have continued to mourn the destruction by Nebuchadnezzar, (the destruction by Titus in A.D. 70 is another matter). It is in fact hard for us to realize how complete the destruction was.
The old “City of David” lies outside the present city walls. This is only partially due to the effects of the destruction by the Romans. The Chaldeans so broke down the Jebusite and Davidic walls and terraces that restoration was impossible; and Nehemiah had to build his wall much higher up the slope, greatly reducing the area of what had been the center of the city. 
There is also no trace in the temple area of anything that can be linked with Solomon, certainly not the “stables” that have been given his name. Even the huge blocks of stone visible at the base of the West (Wailing) Wall are Herodian, not Solomonic.
All this means that at the return from exile, a completely new beginning was needed. Lamentations, in this sense, is a funeral dirge over an irrecoverable past.
Each chapter has 22 sections with 3 verses each. Each section begins with the next letter of the alphabet. It is written to aid memory, yes, but also to show the destruction was complete from A to Z.
As Jeremiah laments over the destruction of Jerusalem. Chapter three, however, is his personal suffering.
His personal sufferings, (Lamentations 3:1-18).
He is depressed, (Lamentations 3:20).
When you are depressed remember:
- There is much more than this life. Turn your focus from the things of this world, and place them on eternal things, (Lamentations 3:22).
- Live one day at a time. Get up each morning and ask for new mercies for this day, (Lamentations 3:23). Do not get into the trap of focusing too far in the future.
- Put your hope in God, not your circumstances. Your confidence must come from God. You must study and meditate on who God is and His wonderful attributes. Study and memorize His Word, study His promises, (Lamentations 3:24).
- Be patient . . . wait on His timing, (Lamentations 3:25-26).