Siberian Railway

The 4,607-mile long Trans Siberian Railway is the longest railway in the world.It runs across Siberia, a vast Asian part of Russia,from Chelyabinsk in the Ural mountains to Vladivostok on the pacific coast.Although studies of projects of the railway date from the mid-19th century,its construction was actually began in the Czarist regime in 1891 and it was opened for use in 1905.The construction of the railroad encountered enormous problems including wide rivers ,steep grades around Lake Baikal,permafrost in Eastern Siberia,extrems of temperature and political turmoil.But all obstacles yielded to human endeavour.Thirty-eight tunnels were cut through the mountains along the shores of Lake Baikal and the all-Russian route,which was completed by 1971,covered a total distance of 5,973 miles from Leningrad to vladivostok.Modernisation of the railway followed in the 1930s.It was originally a single track was laid later and electrification was undertaken soon after.This vast railway was a major element in the settlement of Siberia at the turn of the 20th century.It si a vital artery linking outlying Siberian industrial regions and mining centres with the core economic area of European Russia.

Great wall of China

The Great Wall of China is the largest defence fortification and the greatest building enterprise ever undertaken by man.About 1500 miles long,this unique wall stretches from the Gulf of Chihli of the Yellow sea along the northern frontier of China to Kansu province in the west.The width of this wall varies from 15 to 40 feet at the base,and from 12 to 35 feet at the summit.Its height ranges from 20 to 50 feet.It is the only structure on the earth that can be identified from the moon.
Walled frontires between the kingdoms in China date from at least the 4th century BC.In the 3rd century BC,the first emperor of "Ch'in",after uniting China,linked up the existing walls and built new sections to creat the Great Wall as a continuous unit.His purpose was to defend China from the Hunes on the north.Watch towers and garrison stations were set at regular intervals in order to send singles and guard the bulwark.The wall was constructed in such a way that troops summoned by beacon fire could be quickly transported along its top.
The wall was built mostly of rubble,although the western sections are of tamped earth and important passes are of brick or masonry.The wall was frequently modified in later centuries with new facilities of high towers.Before that,extensive repaires and extensions were mad at various periods,notably during the Ming dynasty.