L’Enfant’s 1791 plan for Washington has been celebrated around the world. Its grand avenues, circles, squares and monumental layout has created an impressive international capital city. But like any city, D.C. has changed over the past two centuries. But a local architect, the Post reports, has determined that in the past century, the District has lost 22 miles of its original street plan. Recent security threats have closed more streets around Capitol Hill and near…