A highly notable and large theatre on Greek ground, the First Ancient Theatre of Larissa was built on the slope of Frourio hill (or 'Fortress' hill), at the fortified citadel of the ancient city. Apparently, it was fitted into the city web of ancient Larissa, as its parodoi (passageways, public entrances) were linked to the city's large processional ways. According to inscription testimonies, the construction dates to the early third century BC. During the first centuries, the theatre served a dual purpose: apart from theatrical performances, it also hosted the assemblies of the senior regional authority, the so called ?Koinon? of the Thessalians. At the end of the first century BC it was transformed into a roman arena and thus stayed in use until the late third century AD, whereas theatrical performances and other events took place in the town's inornate Second Ancient Theatre.

Until recently, the largest part of the theatre had been lying under private plots and residences, but thanks to excavation works in recent years, it came to light almost in its entirety. The huge monument built almost exclusively of marble, has a rich plastic decoration. A natural hill cavity hosted the stepped cavea (gr.: koilo, auditorium) with seats of white marble produced at the old quarry of Kastri hill, at Aghi? district. The diazoma (landing), a 2m wide corridor, divided the cavea into the lower section (main theatre) and the upper section (epitheatro). The major part of the latter has been destroyed, but we know that it was divided by 20 staircases into 22 cunei, comprising 14 to 18 rows of seats each. The epitheatro was narrower on the sides, thus providing enough space for a ramp or staircase. The main theatre was divided by 10 staircases into 11 cunei, each cuneus counting 25 rows of seats. The end of the main theatre, which led to the orchestra, was built out of marble blocks in order to support the tiers. During the theatre's conversion into an arena (first century BC), the first four rows of seats were removed in order to extend the orchestra for another 4m approximately, while on the previous fifth row, which became the first, were placed inscribed re-used marble doorframes. The seats removed were installed under the doorframes for reasons of static. These transformations aimed at the protection of spectators. In front of the main theatre's lowest part, an enclosed conduit, 1m in width, covered with smoothed marble slabs, surrounded the orchestra and penetrated the foundation of the two-exit scene; somewhere behind the scene it would turn to Peneus (Pini?s) river. Although not yet excavated, the orchestra has an estimated diameter over 25m. The two parodoi, together with their retaining walls of smoothed white marble blocks, though not entirely uncovered, are maintained in excellent condition.

The best preserved part is the scene, consisting of four rooms communicating through three entrances, and built in three phases. The first phase (first half of the third century BC) coincides with the construction of the theatre: the walls were built with carved poros stones and were adorned with paintings. The two lateral rooms had independent entries from the south wall and were simply used for storage, while the two internal rooms, communicating through internal doors, served for the preparation of actors (hypokrites). In the second phase (first half of the second century BC), to the side of the orchestra was added the proscenium (front of stage) with a total length of 20m and width of 2m. It had six jambs and six monolithic engaged Doric columns in line, and a Doric entablature on its colonnade; the whole construction was supporting a wooden tribune called ?logeio?, where the actors performed. During the third phase (early first century AD), the scene suffered serious alteration, also related to the conversion of the theatre into an arena. At that time were added luxurious marble overlays, engaged columns, pillars and sculptures, as well as a second floor, but present evidence about its form is sparse.

The upper part of the theatre was visible until the mid nineteenth century; yet, after the earthquake in Larissa in 1868, the cavea was covered by the ruins of brick houses destroyed, while new buildings were built on the consequent embankment. Moreover, as long as the monument had been visible, many of its stones were removed to be used as building material. In order to uncover the theatre, the then Ephor of Antiquities Apostolos Arvanitopoulos started the excavations in 1910, and brought to light part of the scene. The revelation of the monument was largely due to the broader expropriation programme that began in 1990, continued in 1998 and was completed in the year 2000.