City Usti nad Labem. View of the medieval castle Strekov from the observation deck of the castle Vetruse. Strekov Castle is located on a rocky mountain about 100 meters high, located on the right bank of the river Laba. Since the XIV century, he changed many owners. Strekov described the castle in his letters of Johann Wolfgang von Goethe, the gloomy walls of the castle inspired Wagner when he wrote the opera Tannhäuser.