Porvoo Cathedral is a 15th-century Gothic church. The church only became a cathedral in 1723 when the diocese of Vyborg was transferred to Porvoo. The Cathedral is known to have temporarily become the "Parliament of Porvoo", opened in the Cathedral in 1809. It was in this setting that the declaration of the sovereign Alexander I (1801-1825) took place, transferring the eight former provinces of Sweden that constitute Finland to the power of the Russian emperor.
Little or nothing is known about the Master of Pernå, a master builder, probably of German origin, who worked from the 1430s to the 1460s. However, this church builder has left an important trace in the Finnish religious heritage as he is known to be the builder of some of the most beautiful medieval churches in Finland.
The Pernå Church is a medieval religious building that was probably built between the 1410s and 1440s. The interior of the church bears traces from several eras: the baptismal font is from the 14th century, the crucifix from the 15th century, a fragment of the crucifix dates from the 17th century, the pulpit and the altar cabinet are from the 1650s and so on. The church also has frescoes, most of which date from the 1440s. The bell tower of the church of Pernå was built in 1853. The stained glass windows in the church date from 1939 and were designed by Lennart Segerstråle.
Pyhtää Church is a medieval stone church dating from the 1460s and is one of the best-preserved medieval churches in Finland. In 1670, the church was severely damaged by fire. The bell tower was built in 1820 according to drawings made in 1818. One of the only exterior constants of the building was its medieval facade, which has remained practically unchanged. The church has original medieval vaults and wall paintings as well as wood carvings. The altarpiece was painted by Auguste Joseph Desarnod and was donated to the church in 1848.
The Church of St. Lawrence is a medieval stone church that was built in the middle of the 15th century and dedicated to St. Lawrence of Rome. A fire severely damaged the church in 1893, and the facade underwent extensive changes. The church is now a mixture of styles from the Middle Ages and the neo-Gothic of the 1890s. Before the fire, the belfry consisted of three cube-shaped floors: a medieval stone floor, a brick floor from the 1820s and a third wooden floor for the clock. The top floor was destroyed in the fire and a new second floor, twice as high, in Gothic Revival style was therefore made.
The old church of Sipoo, or St. Sigfrid's Church, is a medieval stone church built between 1450 and 1454. The bell tower was built in the Baroque style in the 18th century and was originally made of wood. The present stone base was built in 1811. The building was restored in the 1930s, without completely recovering its original form. Inside, the arches are decorated with simple paintings from the Middle Ages, some of which appear as symbols of pagan origin.
St. Mary's Church is first mentioned in 1396 but the present stone church was probably built between 1430 and 1470. The church was burglarised and burned down twice during wars in the 16th century. The decorations on the vaults and walls were damaged and other valuables were lost. The church burned again in the fire of Hamina in 1821. The Gothic building was later renovated by Carl Ludvig Engel in the Imperial style and completed in 1828.