ISTANBUL

Istanbul is historically known as Byzantium and before 1924 as Constantinople, is the most populous city in Turkey and the country's economic, cultural, and historic center. Istanbul is a transcontinental city in Eurasia, straddling the Bosporus strait (which separates Europe and Asia) between the Sea of Marmara and the Black Sea. Its commercial and historical center lies on the European side and about a third of its population lives on the Asian side.

The city is the administrative center of the Istanbul Metropolitan Municipality (coterminous with Istanbul Province), and with a total population of around 15 million residents, Istanbul is one of the world's most populous cities and ranks as the world's fourth-largest city proper and the largest European city. Istanbul is viewed as a bridge between the East and West.

Geography

Istanbul is located in north-western Turkey within the Marmara Region on a total area of 5,343 square kilometers (2,063 sq mi). The Bosphorus, which connects the Sea of Marmara to the Black Sea, divides the city into a European, Thracian side—comprising the historic and economic centers—and an Asian, Anatolian side.

The city is further divided by the Golden Horn, a natural harbor bounding the peninsula where the former Byzantium and Constantinople were founded. The confluence of the Sea of Marmara, the Bosphorus, and the Golden Horn at the heart of present-day Istanbul has deterred attacking forces for thousands of years and remains a prominent feature of the city's landscape.

Climate

In the Köppen–Geiger classification system, Istanbul has a borderline Mediterranean climate (Csa), humid subtropical climate (Cfa) and oceanic climate (Cfb), due to its location in a transitional climatic zone.

Since precipitation in summer months ranges from 20 to 65 mm (1 to 3 in), depending on location, the city cannot be classified as solely Mediterranean or humid subtropical. Due to its size, diverse topography, maritime location and most importantly having a coastline to two different bodies of water to the north and south, Istanbul exhibits microclimates. The northern half of the city, as well as the Bosporus coastline, express characteristics of oceanic and humid subtropical climates, because of humidity from the Black Sea and the relatively high concentration of vegetation.

The climate in the populated areas of the city to the south, located on the Sea of Marmara, is warmer, drier and less affected by humidity. The annual precipitation in the northern half can be twice as much (Bahçeköy, 1166.6 mm), than it is in the southern, Marmara coast (Florya 635.0 mm).  

There is a significant difference between annual mean temperatures on the north and south coasts as well, Bahçeköy 12.8 °C (55.0 °F), Kartal 15.03 °C (59.05 °F). Parts of the province that are away from both seas exhibit considerable continental influences, with much more pronounced night-day and summer-winter temperature differences. In winter some parts of the province average freezing or below at night.

Architecture

Istanbul is primarily known for its Byzantine and Ottoman architecture, but its buildings reflect the various peoples and empires that have previously ruled the city. Examples of Genoese and Roman architecture remain visible in Istanbul alongside their Ottoman counterparts.

Nothing of the architecture of the classical Greek period has survived, but Roman architecture has proved to be more durable. The obelisk erected by Theodosius in the Hippodrome of Constantinople is still visible in Sultanahmet Square, and a section of the Valens Aqueduct, constructed in the late 4th century, stands relatively intact at the western edge of the Fatih district.The Column of Constantine, erected in 330 CE to mark the new Roman capital, stands not far from the Hippodrome.

Early Byzantine architecture followed the classical Roman model of domes and arches, but improved upon these elements, as in the Church of the Saints Sergius and Bacchus. The oldest surviving Byzantine church in Istanbul—albeit in ruins—is the Monastery of Stoudios (later converted into the Imrahor Mosque), which was built in 454.

Among the oldest surviving examples of Ottoman architecture in Istanbul are the Anadoluhisarı and Rumelihisarı fortresses, which assisted the Ottomans during their siege of the city. Over the next four centuries, the Ottomans made an indelible impression on the skyline of Istanbul, building towering mosques and ornate palaces.

The largest palace, Topkapı, includes a diverse array of architectural styles, from Baroque inside the Harem, to its Neoclassical style Enderûn Library. The imperial mosques include Fatih Mosque, Bayezid Mosque, Yavuz Selim Mosque, Süleymaniye Mosque, Sultan Ahmed Mosque (the Blue Mosque), and Yeni Mosque, all of which were built at the peak of the Ottoman Empire, in the 16th and 17th centuries. In the following centuries, and especially after the Tanzimat reforms, Ottoman architecture was supplanted by European styles. An example of which is the imperial Nuruosmaniye Mosque.

Areas around İstiklal Avenue were filled with grand European embassies and rows of buildings in Neoclassical, Renaissance Revival and Art Nouveau styles, which went on to influence the architecture of a variety of structures in Beyoğlu—including churches, stores, and theaters—and official buildings such as Dolmabahçe Palace.

I think Istanbul is the heart of the World brings about its  Architecture, history and all other things. The city has been the capital of many important empires like Byzantine and Ottoman Empire so if you want to see amazing structure and view you should go to Istanbul.