Theatre of Clunia Sulpicia
The theatre is the most significant structure to survive at Clunia. Carved out of rock, it had a capacity of 10,000 spectators, which made it one of the biggest of its time in Hispania. It was intended to house performances of theatrical works of the classical period. (Wikipedia)
Please notice the two small figures on the bottom left, they are my sister and her daughter.
I do not know about the quality of the performances in this theatre, but I know the views from the highest seats is really wonderful!