Košťálov is a ruined donjon-type castle in the western Czech Central Uplands near Třebenice. First mentioned in 1372 documents, it likely dates back to the early 14th century. The Kaplíř family associated with it used it as a noble residence until the early 17th century. It has been protected as a cultural monument since 1964.

The castle's origins trace to the early 14th century when Bohemia was part of the Holy Roman Empire under King John of Luxembourg. Although its exact construction date is undocumented, historical sources suggest it may have been built in that period's first half. The earliest known mention dates to 1372, with Aleš mladší ze Slavětína as one of its early owners. While specific details about its initial builders are unknown, Košťálov is often linked to prominent families like the Kaplířové ze Sulevic.

Architecturally, it features a donjon-type structure with distinct upper and lower wards. The main residential and defensive building was a three-story rectangular palace in the upper ward. This palatial structure included a second-floor knight's hall with four windows on opposing sides. The lower ward contained at least two residential buildings and other economic structures, all fortified for domestic and defense purposes.

Ownership transitioned through several notable families over centuries. Initially associated with Aleš mladší ze Slavětína in the late 14th century, it later became linked to the Kaplíř family by at least the late 15th century. By 1486, three brothers from this family divided its spaces for residence: Zdislav in the upper ward's palace and Dobeš and Jan each in separate buildings within the lower ward. The castle remained under their ownership until 1609 when Adam ze Vchynic acquired it.

Throughout its history, Košťálov witnessed significant events such as a Hussite army near its vicinity during the Hussite Wars in 1422. This period marked religious and military upheaval across Bohemia. Despite these turbulent times, the castle continued to serve as a noble residence until gradually falling into disuse by the early 17th century.

Today, Košťálov stands as a cultural monument, though its condition reflects years of neglect. The upper palace's walls are deteriorating, and many architectural details have been lost over time. Vegetation has overtaken parts of the site, making some areas challenging to access. Despite these challenges, the castle remains an intriguing destination for visitors interested in history and architecture.

Košťálov offers a glimpse into medieval life and the strategic importance of such structures during their prime. Its romantic location within the scenic Czech Central Uplands adds to its allure, making it a worthwhile visit for those fascinated by historical ruins and the stories they hold. The castle's connection to notable figures like Karel Hynek Mácha and Emil Filla further enhances its cultural significance, inviting visitors to explore its storied past.