Where is the largest cenotaph in the world located?

The largest cenotaph in the world is located in Washington, D.C. This structure is known as the Washington National Cathedral's American Memorial, often referred to as the cenotaph for Franklin Delano Roosevelt, but there may be some confusion because a cenotaph is generally understood as an empty tomb or monument erected in honor of a person whose remains are elsewhere.

Washington, D.C., with its numerous memorials and monuments, serves as the nation's capital and symbolizes significant national remembrance. The cenotaph in this city commemorates all president's contributions and honors their legacy, which showcases the country's gratitude and recognition of its leaders and historical figures.

The other locations mentioned have notable memorials and cenotaphs, but they do not surpass the scale and significance of the one in Washington, D.C. This context reinforces the choice of Washington, D.C. as the answer, highlighting its unique role in national commemoration.