What at first appears to be a stele and two small ruined buildings just off the dirt road is actually the sprawling site of a city that was once an important stop between the Aksumite capital (in modern Ethiopia) and the port city of Adulis on modern Eritrea's Red Sea coast. There's no signage explaining the ruins and no guide on hand to show you around, but a wander through the crumbling ruins is certainly evocative.
The site is about 1.5km south of Senefe. Turn left onto the dirt road just after exiting town, when the highway curves. Look for the broken stele in the middle of the road, and the first buildings are just on your right.