Scotland Travel: Blair Castle. The oldest part of the castle is the six-storey Cummings or Comyn's Tower, which may retain some 13th-century fabric, though it was largely built in the 15th century. The extensions which now form the central part of the castle were first added in the 16th century. The apartments to the south were added in the mid-18th century to designs by architects John Douglas and James Winter. The south-east range, incorporating the clock tower, was rebuilt by Archibald Elliot after a fire in 1814. Finally, the castle arrived at its present form in the 1870s, when David Bryce remodelled the whole building in a Scots Baronial style, and added the ballroom. The castle has been open to the public since 1936. Its many rooms feature important collections of weapons, hunting trophies, souvenirs of the Murray clan, ethnographica, paintings, furniture, and needlework collected by the Murray family over many generations. The castle also provides the garrison for the Atholl Highlanders, the private army of the Duke of Atholl, noted as the only legal private army in Europe. The Castle and the Atholl Estates were used in the 2008 reality television series Conquer the Castle. In 2009, a Grand Fir (Abies grandis) in Diana's Grove in the grounds of the castle, was measured at 62.7 metres (206 ft), and declared the second-tallest tree in Britain.