A concrete barrier built by East Germany across the border between East and West Berlin to stem the flood of over 2 million refugees fleeing west.

The uprising in Russia in March 1917, in which the Czarist government collapsed and a provisional government was established.

An ancient trade route between China and the Mediterranean Sea extending some 4,000 miles and linking China with the Roman Empire.

An economy that operates by voluntary exchange in a free market and is not planned or controlled by a central authority; a capitalistic economy.

a system in which goods are owned in common and are available to all as needed or a theory advocating elimination of private property

A network of railways connecting Moscow with the Russian Far East. With a length of 5,772 miles, from Moscow to Vladivostok, it is the longest railway line in the world.

a level or rolling treeless plain that is characteristic of arctic and subarctic regions, consists of black mucky soil with a permanently frozen subsoil, and has a dominant vegetation of mosses, lichens, herbs, and dwarf shrubs

one of the vast usually level and treeless tracts in southeastern Europe or Asia

a dense growth of trees and underbrush covering a large tract