I remember a few short years ago when one of the Crystal City properties was a Cat 4. It was the last Cat 4 with direct access to the Metro to get into DC. Now it's all Cat 5's (unless something has changed) and up...unless there's one well out into the suburbs that I'm not aware of.
Only reason I know this is because I used Cat 4 Free Night certs from various promos there a few times.