The principal feature of the tomb is an architecturally unusual cast iron cage, designed by Albert Lybrock and installed in 1859 after Monroe's body was moved from Marble Cemetery in New York City.

Surrounding the sarcophagus is an elaborate Gothic Revival cast iron "cage", measuring about 9 by 13 feet (2.7 m × 4.0 m).

The state appropriated funds, and Monroe's remains were transported to Richmond aboard the steamship Jamestown.

The tomb is considered architecturally significant first for the scale of its use of cast iron, a material not commonly used at that time for that purpose, and for delicacy and degree of flamboyancy achieved in its creation, which could not have been done in stone.

Almost forty percent of the tomb's cast iron structure was repaired and returned to a color closer to its original state.