Kosmonosy Castle is located in Kosmonosy near Mladá Boleslav. It dates back to the second half of the 16th century, built by Krajíři z Krajku. The castle showcases architectural and cultural transformations over centuries. Its current baroque appearance results from renovations by Černínové z Chudenic in the late 17th and early 18th centuries. In the 19th century, the Mirbach family added an Empire-style southern wing.

The origins of Kosmonosy Castle are tied to religious and political upheavals during the Reformation and Counter-Reformation across Bohemia and Europe. Initially a Renaissance structure, it was renovated by Adam Krajíř z Krajku around 1571. The castle's early history reflects broader socio-political dynamics, serving various noble families involved in regional governance.

Architecturally, Kosmonosy Castle began as a Renaissance edifice before transforming into its current baroque form under the Černín family. Heřman Jakub Černín led this transformation between 1697 and 1709 with architect Giovanni Battista Alliprandi's guidance. The castle features a single-story, four-winged building with thirteen window axes on each side, accentuated by two-story pyramidal towers at its corners. Baroque facades are adorned with bossed pilasters and windows topped by suprafenestras with wavy cornices. An Empire-style southern wing was added later in the 19th century by the Mirbach family.

Throughout history, Kosmonosy Castle has seen a succession of notable owners. Initially built by Krajíři z Krajku, it passed through several hands, including Černínové z Chudenic, who were instrumental in its baroque transformation. The Hrzán z Harasova family acquired the castle in 1740, followed by Martinicové and later the Mirbach family, each contributing to its architectural evolution. In the early 20th century, the Klinger family owned it before it became a public educational facility.

The castle's history includes significant events during the Thirty Years' War in the early 17th century when it served as a military occupation site. Generals Johan Banér and Lennart Torstenson used it as a command post in 1639. Eva z Hohenlohe's involvement in the Bohemian Revolt led to its temporary confiscation. Another notable event was the death of Wolfgang Adam, son of Gottfried Jindřich z Pappenheimu, from wounds sustained at a duel near Prague.

Today, Kosmonosy Castle is protected as a cultural monument since 1967 and serves as an educational institution housing a primary school and an economic high school. Its grand hall functions as a concert venue, while several rooms have been adapted for residential use. The castle's rich history and architectural beauty make it a worthwhile destination for visitors interested in exploring Bohemian heritage.

Kosmonosy Castle stands not only as a monument to its past but also as a living part of the community, inviting exploration and appreciation from those who visit. Its historical significance and architectural splendor offer a unique glimpse into the cultural tapestry of Central Bohemia, making it an essential stop for anyone interested in history and architecture.