It is breathtaking to see the ancient theathre hidden among the appartments. But after you get over the ancient-modern shock there isn't really much to see. It is only open in specific periods but you can see everything from the outside as well.It is not protected very much so you won't feel the excitement of seeing the coliseum for example. But it gives a good idea of what Teramo used to be like in those periods. It will take you max 15 minutes to go, see and come back. I advise you to see it.