The main floor is elaborately built, because the most important rooms are there. The architecture of the Kuressaare convent building is unique in Estonia from the aspect of the rooms’ distribution and stone carved decorations. In the other buildings of this kind the rooms are distinctly separated into naves, aisles and bays of vault. But in the festive rooms in Kuressaare the decorative elements are ribbed vaults.

Ascending the staircase to the main floor, there's the cloister. It's a gallery surrounding the courtyard on four sides and connecting all the rooms of the main floor.

It's considered one of the most beautiful archways in the late Gothic style in Old-Livonia. In the south-western and north-western wing original profiled ribs of the cross vaults spring from the walls. Characteristic Gothic windows with pointed arches and restored stone carved window frames open into the courtyard.

On the walls hang the coats-of-arms carved out of dolomite, once belonging to the Saaremaa noblemen and dating from the beginning of the 20th century. In the north-western wing we find a stone piscina – a ritual place for washing hands. Next to it a portal with profiled jambs, opening into the main hall of the castle – the Festive Refectory.

Refectory

The Festive Refectory is a hall with two aisles, which was evidently designed shorter. The north-western pillar differs from the others. The vaults are covered with strong profiled groins giving the room special spaciousness. The aim of the massive octagonal table round the pillar in the south-eastern part is not very clear. Evidently the sessions of the cathedral chapter – consisting of high ranking clergymen were sometimes held there.

At the beginning of the 20th century the noblemen of Saaremaa adapted the room for holding the Landtag. The Neo-Gothic doors made in Riga date from the same period.

The medieval look of the room was restored in 1976. Today it's used as a splendid concert hall with good acoustics. The chairs in the hall are made by local masters according to a century-old designs.

In the south corner of the convent building a chapel – the highest room in the castle is situated. It is a square room with a slender octagonal central pillar supporting the vaults. In the south-western wall of the chapel there is a big and in the south-eastern part a small sacramental niche.

Both of the niches are elaborately decorated. There's a medieval altar table that has suffered from the effect of the time. The stone pulpit in the north-eastern wall is from a later period. Three stone plates made by craftsman Reynken from Tallinn in about 1515 are part of the north-western wall of the chapel. On the middle one we see the symbol of the bishopric and the castle – an eagle.

The living-quarters of the bishop is in the north-western wing. The corner room and the bedroom formed one room. Simple vaults cover these rooms, supported by octagonal pillars. Many pillars have decorations of triangular pyramid carvings. The upper parts of the pillars in the dormitory are nose-shaped, but the foundations are analogical to the pillars in the Refectory. A part of the room is separated by heavy walls into a peculiar windowless sanctuary, that could safely be closed from inside.

This room with a stone platform inside was the bishop’s private area. That room has a connection to the murder of Bishop Heinrich III in the castle in 1381. The bishop was strangled by canon Hermann Bolne during a quarrel. Owing to this fact Kuressaare castle was first mentioned in the chronicles. There's a staircase from the corner room to an extending balcony in the north-western wing. In the same room there's a fireplace (the present design dates from the beginning of the 20th century) decorated with triple orbs and a beautiful coat-of-arms of the castle.

On the walls of the bishop’s quarters are eleven works of Baroque wood carving art from the second half of the XVII century – epitaphs with the coats-of-arms of the Saaremaa noblemen. Making such epitaphs originates from 14th century Germany, where the coat-of-arms of a dead person, after been carried at the head of the funeral procession, was left in the church.

In the XVII century with the development of the Baroque style the coat-of-arms became luxurious and considerably big epitaphs. The task of the epitaph is to keep the memory of a person or a family. The epitaphs exhibited here are brought from the country churches of Saaremaa at the beginning of the 20th century.

In the bigger dormitory in the north-eastern wing there is a big fireplace with the original base restored in 1976 and a door opening into a shaft surrounding the Watchtower and known as the “Lions’ pit”. The legend says that wild animals were kept in the shaft and the convicted prisoners were thrown to them. Actually the door opens into a closed stone gallery, which used to be a medieval toilet. The last and the second hall in the north-eastern wing. This dining-hall is in use as an administrative office of the museum today.