Istanbul is Turkey's largest city and has extensive 4G LTE coverage across both the European and Asian sides. Turkcell is the market leader and has the strongest coverage in Istanbul. Vodafone Turkey and Türk Telekom both cover all main districts.
On the European side: Sultanahmet (Hagia Sophia, Blue Mosque, Topkapi Palace) has strong 4G outdoors. The Grand Bazaar (Kapalıçarşı) has good 4G inside the market. The Spice Bazaar (Mısır Çarşısı) in Eminönü has 4G. Taksim Square and Istiklal Avenue have excellent 4G and growing 5G. Beşiktaş, Ortaköy, and Bebek along the European Bosphorus shore have reliable 4G. Beyoğlu, Karaköy, and Galata have strong 4G.
On the Asian side: Kadiköy has very good 4G throughout the market, ferry terminal, and main streets. Üsküdar is well covered. The Çamlıca Hill viewpoint has outdoor 4G.
The Istanbul Metro has 4G at stations and in most tunnel sections on newer lines (M2, M3, M4). The older M1 has lighter in-tunnel coverage. The Tünel funicular and Bosphorus tram have outdoor coverage. Marmaray (the undersea cross-Bosphorus rail tunnel) has 4G at stations and in tunnel sections.
Istanbul Airport (IST), the mega-airport in northwest Istanbul, has 4G throughout all terminals. Sabiha Gökçen Airport (SAW) on the Asian side also has 4G. South African travellers should ensure their handset is unlocked and supports the local network frequencies.