525 years of Ivangorod fortress (Russia 2017)

Souvenir Sheet 525 years of Ivangorod fortress it reflects the thematic directions:

An anniversary is the date on which an event took place or an institution was founded in a previous year, and may also refer to the commemoration or celebration of that event. For example, the first event is the initial occurrence or, if planned, the inaugural of the event. One year later would be the first anniversary of that event. The word was first used for Catholic feasts to commemorate saints. Most countries celebrate national anniversaries, typically called national days. These could be the date of independence of the nation or the adoption of a new constitution or form of government. The important dates in a sitting monarch's reign may also be commemorated, an event often referred to as a "Jubilee".

A fortification (also called a fort, fortress, fastness, or stronghold) is a military construction designed for the defense of territories in warfare, and is used to establish rule in a region during peacetime. The term is derived from Latin fortis ("strong") and facere ("to make").

A museum (/mjuːˈziːəm/ mew-ZEE-əm) is an institution dedicated to displaying and/or preserving culturally or scientifically significant objects. Many museums have exhibitions of these objects on public display, and some have private collections that are used by researchers and specialists. Compared to a library, a museum hosts a much wider range of objects and usually focus around a specific theme such as the arts, science, natural history, local history, and other topics. Public museums that host exhibitions and interactive demonstrations are often considered to be tourist attractions, and many museums attract large numbers of visitors from outside their host country, with the most visited museums in the world regularly attracting millions of visitors annually.