When architects, developers, and laborers set about transforming the former Columbia Hospital for Women into the massive Columbia Residences complex at the intersection of 25th Street, L Street, and Pennsylvania Avenue NW, they placed the area within a protective cocoon of chain-link fences. Inside the fences, just across L Street from the back door of Marcel’s restaurant, went a little-known monument commemorating a joint international agreement to reduce military forces patrolling the Great Lakes. With…