The Episcopal stronghold and cathedral in Haapsalu was started in the thirteenth century. It changed according to development of weapons and reached its final form in the 16th century. Some of the walls are close to 6 ft. (1.8 meters) thick. The castle was partially demolished during the Great Northern War in 1710 and remained in ruins thereafter.
According to the legend, a canon fell in love with an Estonian girl and brought her secretly into the castle. When discovered, she was walled into a cavity in the chapel and now appears as the White Lady on full moon nights in August to prove the immortality of love.