There have been some fortifications in Lappeenranta city from the 17th century. After the defeat of Sweden-Finland in Great Northern War 1700-1721 Viborg castle and large areas in Carelia were lost to Russia. The military value of Lappeenranta, the new border city, was suddenly increased. The construction of the new bastion fortress was started immediatelly after war in 1721. It was planned to be a part of the new defence system of Finland together with Olavinlinna castle and Hamina fortress.
Russians conquered the fortress in the next war in 1741 after bloody battle. New border was moved to west and Lappeenranta was left to Russian side. Russians settled a garrison to fortress and started to enhance it in the 1750's and again in 1791-1792. After the Finnish War in 1808-1809 fortress lost its military value. After year 1810 it was used as a garrison and prison. During the Finnish Civil War in 1918 red guards were arrested and executed in Lappeenranta fortress.
Nowadays fortress has been renovated and open for visitors. The former garrison buildings are now home to the South Karelian Museum and Art Museum, artists' and craft workshops, Lappeenranta's Orthodox church and parish hall, a children's art school and a café, among others.
Sweetheart Abbey was a Cistercian monastery, founded in 1275 by Dervorguilla of Galloway in memory of her husband John de Balliol. His embalmed heart, in a casket of ivory and silver, was buried alongside her when she died; the monks at the Abbey then renamed the Abbey in tribute to her. Their son, also John, became king of Scotland but his reign was tragic and short. The depredations suffered by the Abbey in subsequent periods, have caused both the graves to be lost. The abbey, built in deep-red, local sandstone, was founded as a daughter house to Dundrennan Abbey; this Novum Monasterium (New Monastery), became known as the New Abbey.
The immediate abbey precincts extended to 120,000 m2 and sections of the surrounding wall can still be seen today. The Cistercian order, also known as the White Monks because of the white habit, over which they wore a black scapular or apron, built many great abbeys after their establishment around 1100. Like many of their abbeys, the New Abbey's interests lay not only in prayer and contemplation but in the farming and commercial activity of the area, making it the centre of local life. The abbey ruins dominate the skyline today and one can only imagine how it and the monks would have dominated early medieval life as farmers, agriculturalists, horse and cattle breeders. Surrounded by rich and fertile grazing and arable land, they became increasingly expert and systematic in their farming and breeding methods. Like all Cistercian abbeys, they made their mark, not only on the religious life of the district but on the ways of local farmers and influenced agriculture in the surrounding areas.
The village which stands next to the ruins today, is now known as New Abbey. At the other end of the main street is Monksmill, a corn mill. Although the present buildings date from the late eighteenth century, there was an earlier mill built by and for the monks of the abbey which serviced the surrounding farms.