The Roman Odeon, the most significant ancient monument in Patras, is in the upper town and was built around 160 AD, in the reign of either Antoninus Pius or Marcus Aurelius. It was severely destroyed by successive invasions, wars, and earthquakes. It was almost buried under the remains of other buildings and ground. It was in 1889 when the Odeon was found by accident while some workers were digging up the ground for the construction of the port. It has been restored and partially reconstructed, and is used as an open-air theatre for performances and concerts in the summer.
Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.