The Barclay de Tolly Mausoleum commemorates one of the most famous Russian commanders who fought Napoleon in 1812 and 1813 and who culminated his triumph with a march through Paris in March 1814. His family was partially of Scottish extraction but from the 17th century had lived in what is now Latvia and Lithuania. Following the Russian conquest of Finland in 1809, he was the first governor-general there until 1812.
Jõgeveste was the estate of his wife's family and his body was brought back there after his death in East Prussia in 1818. The mausoleum was completed in 1823 on the instructions of de Tolly's wife Eleanor von Smitten. She commissioned Apollon Shchedrin, a leading St Petersburg architect, to design it and its structure has remained intact since then, although the two coffins were opened during World War II. The exterior design suggests parallels to a Roman triumphal arch, the interior to a chapel with an altar recess where the bust of de Tolly is placed. The statue on the right is of Athena, the Greek goddess of war, and on the left the statue of a sitting woman represents the symbol of mourning. Outside are the tombs of de Tolly's son and daughter-in-law and a Soviet memorial to soldiers killed in the 1944 invasion of Estonia.
Ängsö Castle was first named as "Engsev" in a royal charter by king Canute I of Sweden (r. 1167-1196), in which he stated that he had inherited the property after his father Eric IX of Sweden. Until 1272, it was owned by the Riseberga Abbey, and then taken over by Gregers Birgersson.
From 1475 until 1710, it was owned by the Sparre family. The current castle was built as a fortress by riksråd Bengt Fadersson Sparre in the 1480s. In 1522, Ängsö Castle was taken after a siege by king Gustav Vasa, since its owner, Fadersson's son Knut Bengtsson, sided with Christian II of Denmark. However, in 1538 it was given by the king to Bengtsson's daughter Hillevi Knutsdotter, who was married to Arvid Trolle.
In 1710, the castle was taken over by Carl Piper and Christina Piper. Ängsö Castle was owned by the Piper family from 1710 until 1971, and is now owned by the Westmanna foundation. The castle building itself was made into a museum in 1959 and was made a listed building in 1965. It is currently opened to visitors during the summers.
The castle is a cubical building in four stores made by stone and bricks. The lower parts is preserved from the middle ages. It was redecorated and expanded in the 1630s. The 4th storey as well as the roof is from the expansion of Carl Hårleman from 1740-41. It gained its current appearance in the 1740s.