northbound 3rd street tunnel, two left lanes blockedha by t work zone.ne right lane getting by. >> thank you, melissa. when your favorite animal is a panda, it's not every day you get to see one up close. well, yesterday i came within arms reach at the national zoo. i didn't touchhim. we got exclusive behind the scenes access for one of d.c.'s most famous residents. >> hello. >> for a 275 pound giant panda, tian tian as an agreeable patient. >> so excited today. >> he fathered three b cubsn at the national zoo. at 21, he is consideredn older bear and vets have to perform routine check ups to make sure he stays healthy. >> you might equate him to a human entering retierement stag of life. >> the zoo invited us to watch him get hisnnual cardiac ultrasound. this is the first time he had visitors for this procedure so i was instructed not to speak in case id start him. >> being able to evaluate the heart function in an awake animal makes it more natural situation so we can get better formation that way. him an tian's keepers fed honey water to get him to sit