"Monumental works" refer to large, impressive sculptures, structures, or buildings that hold historical, cultural, or artistic significance. There are several synonyms that can be used to describe such works, depending on their nature. "Landmark" is a commonly used synonym, often used to describe a prominent structure or feature that is easily recognizable from afar. "Majestic" and "imposing" can be used to describe works that evoke a sense of awe and grandeur, while "epic" and "heroic" can be used when referring to works that embody significant cultural or historical events. "Masterpiece" is another synonym that highlights the artistic value of a monumental work, often used to describe works of exceptional quality and intricacy.