The 7 Lakes in Rila Mountains are one of the most popular and beautiful areas in Bulgaria. There is a trail passing by all the lakes. Further up after the Seven Rila lakes are the beautiful Urdini Lakes. Rila Monastery was founded in the 10th century, it is regarded as one of Bulgaria's most important cultural, historical and architectural monuments (Wikipedia). The oldest building remaining today at the site is the tower from the 14th century. UNESCO World Heritage Site.