At Via di Città 126 is the Palazzo delle Papesse’s contemporary art gallery. Besides its permanent collection by Micha Ullman, Perino Vele and Antonio Catelani there are temporary exhibitions. Go up to the terrace to admire the views of town (tel. 0577 2 20 71).
On the same street is the Palazzo Chigi-Saracini (Picture 1). In the 18th and 19th century it was given the Gothic style we all admire today. It is said that from the palazzo’s tower a young boy in the battles between the Sienese and the Florentines told the Sienese hordes below how their side was doing against the Florentines. The Accademia Musicale Chigiana has its base in this palazzo.
The Pinacoteca Nazionale (National Art Gallery) is housed in the Palazzo Buonsignori dating back to the 1300s. It has the most remarkable collection of Gothic masterpieces by artists of the Sienese school. The collection shows the difference between the Byzantine and Gothic Sienese artists and the Renaissance Florentine. Perspective, emotion and movement that the Florence artists had found out how to show in painting were still absent in the Sienese school.
On the ground floor, Rooms 27-32 and 37 have pieces by Mannerist Domenico Beccafumi and Il Sodoma, whose Christ Tied to the Pillar shows him in tears.
On the first floor, the first two rooms display pre-Gothic pieces. Duccio di Buoninsegna and his followers’ works are displayed in Rooms 3 and 4. The Madonna of Mercy, depicting Mary sheltering society, and Madonna and Child by Simone Martini are also here. Rooms 7 and 8 are devoted to Pietro and Ambrogio Lorenzetti and the other three rooms are dedicated to artists of the early 1400s.
Giovanni di Paolo’s pieces hang in Rooms 12 and 13. A pair of them departs from the typical guidelines of the Sienese school. Lack of gold, some strokes of perspective and emotion and innovative architectural subjects appear for the first time in Presentation of Jesus in the Temple
Nearby the Pinacoteca Nazionale is the 13th century Chiesa di Sant’Agostino (tel. 0577 38 57 86; Prato di San Agostino) which was commissioned by the king of Naples and planned by Vanvitelli. Because of the fire in the church, its interior was decorated in the rococo style in the 18th century. The Adoration of the Crucifix by Perugino is in the south aisle and Il Sodoma’s Adoration of the Magi is in the Piccolomini Chapel.
The Gothic Chiesa di San Domenico in the piazza of the same name is stunning, though it has been repeatedly modified throughout its history.
In accordance with the Dominican style, the interior was designed in a simple way. Near the entrance lies the Capella delle Volto, where Saint Caterina’s portrait hangs. It is the place where Caterine made her religious vows and supposedly worked miracles.
In those times it was customary to preserve the body. Thus, Saint Caterina’s head is kept in a tabernacle of the altar in the Cappella di Santa Caterina. Her dried up thumb is also displayed here along with a whip she used for self castigation. The rest of her body is in Rome.
Her house, Casa di Santa Caterina is located on Costa di Sant’Antonio (tel. 0577 22 15 62). The rooms were made into chapels in the 15th century and are frescoed by the Sienese school with events of her life. Some of her belongings and her cell are in different rooms. 
This was her and her large family's house. A passionate devotee to religion from very young age, at 7 she decided to remain a virgin for the rest of her life and when she was a teenager she would go for days without eating. These periods alternated with periods she devoted to taking care of those in need. There are endless letters she dictated to send to powerful figures during the period. She was an influential ambassador for Florence going to Avignon to bring the Pope back to Rome. She died at 33, was canonized about 80 years later, and was named "Doctor" of the Church in the 20th century.
Fortezza Medicea or Forte di Santa Barbara (Picture 3) commissioned by Cosimo I de Medici in the 16th century is a classical fortress dating from the beginning of the Grand Duchy when Florence had taken control of Siena.
Head for the Loggia dei Mercanzia dating from the 15th century which used to be crowded with merchants doing business in the old times. Then head east along Banchi di Sotto to observe the Renaissance Palazzo Piccolomini (Picture 2), the city´s archive. Continue eastwards to find Pietro Lorenzetti’s frescoes in the 13th century Basilica di Santa Maria dei Servi and the Porta Romana built in the 1300s.
Departing again from the Loggia dei Mercanzia along Banchi di Sopra is the 13th Palazzo Tolomei at the edge of the square of the same name. Then heading north you reach Piazza Salimbeni flanked by Palazzo Tantucci, Palazzo Salimbeni in the Gothic style and the Palazzo Spannocchi in the Renaissance style and fronted by 29 busts watching over observers.
From the Piazza Salimbeni going northeast on Via dei Rossi you find the Chiesa di San Francesco which was used as barracks and survived a fire. Nextdoor is the Oratorio di San Bernardino (tel. 0577 28 30 48; Piazza san Francesco 9) where there are frescoes by il Sodoma and a museum displaying religious works.