concrete buildings proliferated. Istanbul experienced a population explosion due to immigration, and within a very short period it expanded far beyond the historical city walls. The areas inside the walls were invaded by workshops, mills and offices; even the new thoroughfares could not solve the traffic problems, and the inadequacy of the infrastructure gave rise to a sea pollution problem, starting with the Golden Horn.
With the initiatives for saving the city in the 1980s, Istanbul embarked on a process of restructuring on a scale unseen in its history.Thousands of buildings along the Golden Horn were demolished to make way for a green belt on its shores; parks and gardens were built on the land claimed by filling up the beaches of the Sea of Marmara. In order to prevent sea pollution drainage systems were completed and physical and biological wastewater treatment plants were erected; the use of natural gas for heating has considerably reduced air pollution. Efforts are continuing for the restoration of the Roman city walls, and Beyoglu, the main artery, was rescued by building a newavenue. Improvements were made in ihe general cleaning, maintenance, garbage collection fields and these services are now at Western European standards. Ring roads cross the Bosphorus over two suspension bridges to connect the two continents. The European side has now a fast tramway system and a subway, and comfort and speed has been ensured in sea transportation with the hydrofoil terminals built on the seashores. All industrial establishments on the historic peninsula have been moved to new facilities in the suburbs, and the new international bus terminal has reduced traffic intensity. The old jail and the first large concrete building of the city were given over to tourism and converted into 5-star hotels.
The city is growing dynamically and developing at full speed on an east-west axis along the shores of the Marmara.