The most important are clustered around three adjoining the triangular Piazza della Ceterna named after the city's 13th-century travertine well, surrounded by elegant palaces; the Piazza del Duomo, grouping church and town hall as the center of civic and religious power; and the Piazza delle Erbe ?market place with twin Salvucci towers.

Does it follow that "The Salvucci towers are open to visitors."?
Available options:
- yes;
- it is not possible to tell;
- no;
it is not possible to tell