york castle fell into disrepair by the 15th and 16th centuries, becoming used increasingly as a jail for both local felons and political prisoners. by the time of elizabeth i the castle was estimated to have lost all of its military value but was maintained as a centre of royal authority in york. the outbreak of the english civil war in 1642 saw york castle being repaired and refortified, playing a part in the royalist defence of york in 1644 against parliamentary forces. york castle continued to be garrisoned until 1684, when an explosion destroyed the interior of clifford's tower. the castle bailey was redeveloped in a neoclassical style in the 18th century as a centre for county administration in yorkshire, and was used as a jail and debtors' prison. prison reform in the 19th century led to the creation of a new prison built in a tudor gothic style on the castle site in 1825; used first as a county and then as a military prison, this facility was demolished in 1935. by the 20th century the ruin of clifford's tower had become a well-known tourist destination and national monument; today the site is owned by english heritage and open to the public. the other remaining buildings serve as the york castle museum and the crown court.