Nanjing is blessed with a multitude of historical sites. Existing and famous sites featuring ancient cultures in Nanjing include the Hulu Cave Ancient Human Fossil Site at Tangshan, the Shenxian Cave Ancient Human and Vertebral Fossil Site, the Xuecheng Ancient Culture Site, the Beiyinyangying Ancient Culture Site, the Niutougang Ancient Culture Site, the Dianjiangtai Ancient Culture Site, and the Hushu Ancient Culture Site. More specifically, the Hulu Cave Ancient Human Fossil Site at Tangshan is the only ancient human fossil site to be discovered in the southeast part of the lower reaches of the Yangtze River in China, dating the history of human activity in the Nanjing area to 500,000 years ago. In 473 BC, a city was built southwest of what is currently Zhonghuamen after the Wu State was annihilated by the Yue State, marking the commencement of Nanjing's history as a city. The existing city sites include Shitoucheng Site, the Site of the Capital of the Six Dynasties, the Site of the Palace of the Six Dynasties, the Nanjing City Wall and its 13 gates, hundreds of ancient tombs, the Qianfoyan Grottoes, the Mausoleum Stone Carvings of the Southern Dynasties, the Yangshan Quarry, and Tianfashenchen Stele. Shitoucheng Site is what remains of the facilities of the Six Dynasties for city defense, and it was also the largest and most important walled city on the periphery of Jiankang during the period of the Six Dynasties. The Site of the Capital of the Six Dynasties is historically and regionally distinctive in terms of its structure, layout, construction philosophy, and defense system, and it also plays a critical role in the history of the development of ancient capitals of China. The Site of the Palace of the Six Dynasties is the most remarkable representative of the palace systems and the architectural art from the period of the Wei, Jin, Southern and Northern dynasties. As for Nanjing City Wall, not only is it the longest wall in China, but it is also one of the largest brick city walls in the world. Among all the ancient tombs in the Nanjing area, the Xiaoling Mausoleum of the Ming Dynasty is the most famous, since it declared the first application of the new systems for building imperial tombs in the Ming dynasty and is the most well-preserved ancient emperor's mausoleum in China. Qianfoyan Grottoes is a masterpiece of the art of Southern Buddhism from the period of the Six Dynasties, and is commonly referred to as "Little Yungang Grottoes". The Mausoleum Stone Carvings of the Southern Dynasties are also noteworthy; not only are they a masterpiece of stone carving art in ancient China, but they are also a gem among the whole world's art treasures. Yangshan Quarry is both extremely magnificent and arguably the largest "stele" in the world, and Tianfashenchen Stele is one of the Four Famous Stelae of the Wu Kingdom. There are also many modern and contemporary historical monument sites in Nanjing that are influential and of great significance in China. These include the Jinghai Temple, the Site of the Heavenly-King Palace of the Taiping Heavenly Kingdom, the China Modern History Museum, the Sun Yat-sen Mausoleum, the Meiyuan New Village, the Yuhuatai Martyrs' Cemetery, the Victory Monument of Crossing the Yangtze River Campaign, and the Memorial Hall Commemorating the Victims of the Nanjing Massacre Perpetrated by Japanese Invaders.