If your attention span for poetry only extends to the length of time it takes to read a limerick, you may find yourself challenged if you try to read the Mahābhārata.
This ancient epic Indian poem earns a lasting place in history for a number of reasons, not the least of which is its size. With over 100,000 lines and 1.8 million words, the Mahābhārata holds the record as the longest poem ever written. The 6.5-hour reading of the Mahābhārata can be heard here. An online version of the Mahābhārata can be read here.
The poem is roughly ten times the length of the Iliad and the Odyssey combined. In terms of its value to literature and culture, it has been compared to the works of William Shakespeare.
Authorship of the epic piece is far from certain and it almost certainly was the combined efforts of more than one writer. Primary authorship is frequently attributed to Vyāsa. Some of the oldest parts of the piece are believed to date back to 800-900 B.C. It probably reached its completed form around A.D. 400.
For other examples of insanely-long national anthems, names, books, etc., grab a cup of coffee, make yourself comfortable, and keep reading.