As a time of peace began with the Persians in 448 BC, Pericles undertook an ambitious plan to rebuild the Acropolis. First the Parthenon was built in 438 BC. Then the Propylaea, the Temple of Athena Nike, and the Erecthion followed. For the next four hundred years, the Acropolis change little. A staircase was added by emporer Claudius in AD 52 and the Beule Gate was built during the 3rd century. After the Edict of Theodosius II, Justinian turned the buildings of the Acropolis into churches. In the 13th, 14th, and 15th centuries, the possession of the Acropolis changed hands many times and its buildings were used as citadels and palaces for the dukes and military officials who held it. In the mid 17th century, the Propylaea, used as a powder magazine, was damaged when it was struck by lightening. A short while later, the Temple of Athena Nike was completely removed to make way for the placement of artillery. A short while later, cannon balls and carelessness managed to destroy much of the Parthenon, which had stood intact for the last 2000 years. In the 19th and 20th centuries, an era of restoration and rebuilding began.