Semily consists of four municipal parts (in brackets population according to the 2021 census):[2] The name means "the settlement of semils".

In the middle of the 19th century, the settlement transformed into a wealthy town when the industrialization arrived and the development of rail transport occurred.

[9] Dr. Karel Farský prayer house was built for the Czechoslovak Hussite Church in 1938 and is considered one of the most valuable buildings of modern architecture in the region.

[10] Obecní dům is a large Art Nouveau house built in 1906–1909, which forms a significant landmark in the historic centre of the town.

[13] The Museum and Regional Gallery is located in a historical one-floor house first documented in the early 17th century, where Antal Stašek worked and his son Ivan Olbracht was born.