| The Leaning Tower demonstration never fails to amaze!
With the top removed, the gravitational force acting through the center of mass of the tower falls within the circle of the base. The torque which this force exerts can be countered by torques exerted by the normal forces acting upward on the base. Adding the top makes the line of action of the gravitational force fall outside the circle of the base. This makes it impossible to satisfy the equilibrium condition and the tower tips over in the direction of the gravitational torque.
The tower at the right is in the Smithsonian Institution collection, and came from the District of Columbia Public Schools.
At the left below is a tower at Miami University in Oxford, Ohio, and the one on the right is at Bowdoin College in Brunswick. Maine.
None of the towers are marked with their maker's name.