El coliseo cuenta con ocho escotillas, las que fueron utilizadas en su totalidad como celdas colectivas, albergando cada una entre 300 y 400 detenidos.

En los muros de estas celdas aún se distinguen los grabados hechos por los prisioneros con llaves u otros elementos, en donde se perpetuaron pequeños mensajes, las iniciales de sus nombres, estrofas de canciones y fechas significativas.

Aunque ya comenzaba la primavera cuando llegaron los prisioneros al estadio, la humedad, el cemento y los helados muros hicieron aún más inhóspito y duro su encarcelamiento. Durante esas gélidas noches, los recluidos debían dormir en el suelo y también en baños e improvisados camarotes, que eran compartidos en turnos, sin abrigo alguno, especialmente en los primeros días.  Algunos sectores se inundaban de agua después de una lluvia, y aún en esas condiciones debían mantenerse en el lugar.

Las enfermedades afloraron, las que se agravaban por la falta de alimentación e higiene adecuadas y, por cierto, la brutal violencia física a la que eran sometidos las y los prisioneros a toda hora.

La escasa y a menudo inexistente alimentación era preparada y traída desde el Estadio Militar, ubicado en el Parque O’Higgins. Consistía en un desayuno muy temprano, de un tazón de café de higo con un pan y luego una comida al día, generalmente legumbres, sopa o fideos, alimentos que se encontraban a menudo en mal estado. Al comienzo, la comida no alcanzaba para todos, por lo que los mismos detenidos se organizaron en cuadrillas para distribuirla a los distintos lugares de reclusión, donde cada prisionero tenía que cuidar de su plato y tazón.

Thousands of people, men, women, and children, both Chileans and foreigners, were detained in the stadium, incommunicado and without any formal charges. Not all of them were left-wing militants or even involved in anything. Many people were also arrested on suspicion, or because someone reported them for any reason, simply for being foreigners, for violating curfew, for appearing left-wing, or were caught up in the large general raids on factories and communities. They were workers, farmers, technicians, professionals, and public officials. There were artists, students, housewives, tourists, and even diplomats detained. In the raids, the police and military forces also took the opportunity to arrest well-known common criminals who ended up living with political prisoners and received equal or worse treatment.

On September 11, 2003, the National Stadium was declared a Historical Monument in its entirety.

The coliseum has eight hatches, and all of them were used as collective cells. Each one housed approximately between 300 and 400 detainees. The hatches and dressing rooms were the places of confinement for the male detainees.

On the walls, we can still see the engravings made by the prisoners with keys or other elements. They engraved small messages, their initials, song verses, a date. Although spring was beginning, the humidity, cement, and icy walls made these places even more inhospitable. The nights were freezing, and the prisoners had to sleep on the floor and also in bathrooms and makeshift bunks, which were shared in shifts. After a few days, one blanket was distributed per person. Some areas were flooded with water after a rain, and even under those conditions, they had to remain in place. Diseases emerged, aggravated by the physical violence to which the prisoners were subjected around the clock and the lack of adequate food and hygiene.

The hunger was acute and permanent. The food was prepared and brought from the Military Stadium in O’Higgins Park. It consisted of a very early breakfast of a fig coffee cup with a bread and then one meal a day, usually vegetables, soup or noodles. On more than one occasion, the food arrived in poor condition. At the beginning, the food was not enough for everyone, so the detainees themselves organized into squads to distribute it to the different places of confinement. Each detainee had a plate and bowl to take care of.

Starting on September 22, the detainees began to be taken to the stands. This became a routine of the early morning and later some afternoons, which allowed them to exercise and share among themselves, but also in a «waiting area» where they were called for interrogations and torture.