in a letter from Venice by Paolo Mori (agent of the Duke of Mantua), dated 7 October 1581, which mentions the “boxes of those two purpose-built venues”. Additionally, in Antonio Persio’s Trattato de’ Portamenti (1607), within a passage referring to the years preceding 1593—and in reference seemingly to either the Tron theatre or the Michiel theatre—the author writes that the nobles “had rented almost all the boxes”. With regard to the date of construction of the Tron theatre, and the presence therein of boxes (an innovative feature from both an architectural-theatrical and commercial point of view), it is noted that somewhat opportunely in 1580 a radical change occurred in the language of the Council of Ten relating to these theatrical venues, as for the first time a formula had been attested which implies concerns relating to their structural solidity in that they had to be “strong and safe so that no collapse can happen”. Therefore, it would appear that the innovation given by the introduction of boxes as an integral part of the structure of a theatrical building gave rise within the Council of Ten to safety concerns. This would explain why the Council ordered that experts had to verify solidity in advance to eliminate collapses and consequent accidents or worse. The Tron theatre (together with the one owned by the Michiel family, located near the Grand Canal) was subsequently closed in 1585 by order of the Council of Ten and emptied of any wooden element that had to do with the theatrical nature of the place; the Tron theatre (i.e. the Teatro San Cassiano) was then reopened probably after 1607. Seventeenth century The construction of the theatre in 1637: birth of the world's first public opera house Archive documents refer with some continuity to the use of the Teatro San Cassiano for theatrical performances throughout the 1610s. In 1629 and 1633, two fires destroyed the theatre. No known archival documents mention the theatre in the two years 1634-1635. In 1636, the Tron brothers (Ettore and Francesco, of the ‘branch’ of the San Benetto family) appear to have communicated to the authorities their intention to open a “Theatre for music”, thus clarifying from the outset its function as an opera house. This, in itself, marks a critical turning point in the history of opera: a theatre built specifically to stage music. This is revealed in a document dated 2 May