Meigs himself designed and implemented most of the changes at the cemetery in the 15 years after the war. In 1865, for example, Meigs decided to build a monument to Civil War dead in the center of a grove of trees west of the Lee's flower garden. U.S. Army troops were dispatched to investigate every battlefield within a radius of the city of Washington, D.C. The bodies of 2,111 Union and Confederate dead were collected, most of them from the battlefields of First and Second Bull Run, as well as the Union army's retreat along the Rappahannock River (which occurred after both battles). Although Meigs had not intended to collect the remains of Confederate war dead, the inability to identify remains meant that both Union and Confederate dead were interred below the cenotaph. U.S. Army engineers chopped down most of the trees and dug a circular pit about wide and deep into the earth. The walls and floor were lined with brick, and it was segmented it into compartments with mortared brick walls. Into each compartment were placed a different body part: skulls, legs, arms, ribs, etc. The vault was half full by the time it was ready for sealing in September 1866. Meigs designed a tall, long, wide grey granite and concrete cenotaph to rest on top of the burial vault. The Civil War Unknowns Monument consists of two long, light grey granite slabs, with the shorter ends formed by sandwiching a smaller slab between the longer two. On the west face was an inscription describing the number of dead in the vault below, and honoring the "unknowns of the Civil War". Originally, a Rodman gun was placed on each corner, and a pyramid of shot adorned the center of the lid. A circular walk, centered from the center of the memorial, provided access. A walk led east to the flower garden, and another west to the road. Sod was laid around the memorial, and planting beds filled with annual plants emplaced.