Tallinn Tallinn, the largest city and capital of Estonia (population 440 000). , the largest city in Estonia (population 440 000), is the capital of Estonia and Harju County County in northern Estonia(pop. 620,000). . It is the main gateway to Estonia; the cultural, economic and industrial centre of Estonia. Tallinn Tallinn, the largest city and capital of Estonia (population 440 000). is on the northern coast of Estonia opposite to Helsinki, the capital of Finland.