Despite its relatively friendly façade, the 14th-century Castle has a grim history. It was rebuilt as a prison in the 1820s and remained so until 1954. During WWII, more than 100,000 people suffered here at the hands of Nazi occupiers before being transported on to extermination camps. Hundreds of Jewish and Polish political prisoners had survived here until July 1944, only to be shot mere hours before the Red Army liberated the city.

Since 1957, the castle has housed the Lublin Museum with a collection ranging from silverware and porcelain to woodcarvings and weaponry. The particularly impressive art includes big names (such as Jacek Malczewski) and big pictures, such as the detail-rich Lublin Union of 1569, depicting the merging of Poland and Lithuania. Jan Matejko's seminal work was hidden in various places throughout WWII, and now takespride of place in the very building where the landmark union took place.

Also worth seeing in the foyer of the castle is the curious Devil's Paw, imprinted on the 17th-century table of the Royal Tribunal. The legend explaining its existence relates to a widow who was avenged by a team of devils after being unjustly treated by the Royal Tribunal.

At the eastern end of the castle is its most prized asset - the exquisite 14th-century Chapel of the Holy Trinity, featured on numerous postcards (the photographers must have snuck in a flash and a wide angle lens). The chapel is covered from floor to ceiling with polychrome Russo-Byzantine frescoes. Painted in 1418, only to be later plastered over, they were rediscovered in 1897 and painstakingly restored over a hundred-year period. These are possibly the finest examples of medieval wall paintings in the country, so colour-rich you could lick the paint off the walls.