As the largest free standing stone structure in the, the Monument is truly engineering marvel. There no mortar holding the stones together; the walls are 15 feet thick at its base and 18 inches at the top. On the elevator ride down, visitors can see the commemorative placed inside the Washington Monument from individuals, organizations, states, and nations during stages of construction. day tickets at the Washington Monument Lodge on 15th Street are distributed on a first-come, first-served basis and run out quickly.