What is the synonym of monumental?

Here are some synonyms for "monumental", depending on the context:

General meaning (large, significant):

* Vast

* Immense

* Colossal

* Grand

* Impressive

* Magnificent

* Tremendous

* Huge

* Enormous

* Gigantic

Meaning related to importance or significance:

* Landmark

* Memorable

* Historic

* Epochal

* Significant

* Noteworthy

* Remarkable

* Extraordinary

* Exceptional

Meaning related to effort or difficulty:

* Herculean

* Daunting

* Difficult

* Challenging

* Laborious

* Arduous

The best synonym will depend on the specific context in which you are using the word "monumental".