Tuida was an early Byzantine and medieval fortress, the remains of which are located on the hill of Hisarlaka in the northeastern part of Sliven, which offers a unique view of the 'Sinite kamani' and the city. It is part of the old mountain fortification system, which played an extremely important role in the defence of the Roman Empire, and later of the early Byzantine Empire, as well as the medieval Bulgarian state. Tuida Castle was originally built in the 4th century AD and was in use until the 13th century.
The ancient Argos Theater was built in 320 BC. and is located in Argos, Greece against Larissa Hill. Nearby from this site is Agora, Roman Odeon, and the Baths of Argos. The theater is one of the largest architectural developments in Greece and was renovated in ca 120 AD.
The Hellenistic theater at Argos is cut into the hillside of the Larisa, with 90 steps up a steep incline, forming a narrow rectilinear cavea. Among the largest theaters in Greece, it held about 20,000 spectators and is divided by two landings into three horizontal sections. Staircases further divide the cavea into four cunei, corresponding to the tribes of Argos A high wall was erected to prevent unauthorized access into the theatron and may have helped the acoustics, but it is said the sound quality is still very good today.
Around 120 CE, both theaters were renovated in the Roman style.