This city has seen the development of humanity, and the whole world has played witness to its massive growth over the millennia. It's been the capital of the Roman, Byzantine and Ottoman empires, and thus is known as the "Capital and Capitals." It's had countless poems, love songs, books, written about it.
It's 18km from Istanbul's Ataturk Airport (IST) on the European side to Sultanahmet, or 20km to what's considered the city center in Taksim. To get to the city center from the airport you can also take taxis (35-40TL), HAVATAS express buses (10TL, and leave every half hour except between 1-4am) or IETT public bus 96T (5TL, or 3TL with an Istanbul Card, though it takes 2-2.5 hours). If you're just trying to go to Sultanahmet you can take the metro/tramway (get on metro from the airport all the way to Zeytinburnu and from there switch to the tram that goes towards Kabatas). The airport on the Asian side is Sabiha Gökçen Airport (SAW) and it's 40km away from Taksim. The best way to get to Taksim would be to take HAVATAS (13TL). Taxis are about 80-85TL. Otherwise there's the E3 IETT public bus that goes to 4. Levent, and from there you can take the metro to Taksim. For general transportation within Istanbul, there are many different modes of transport including buses, metro, metrobus, tramways, funicular, ferries, sea buses, cable cars, minibuses, and commuter trains. To reduce transportation costs and also to not have to buy a new ticket for every single journey, you should just buy an Istanbul Card. Taxis tend to be cheaper in Istanbul than in other major world cities (for example it's typically only 13TL to go from Sultanahmet to Taksim) so that's another reasonable alternative.
The main regions of the city for hotels are Taksim, Harbiye, Sultanahmet, Boğaziçi and near the airport. Despite this, you can find some sort of accommodation just about anywhere in the city. Some of the best hotels in the city include the Çırağan Palace Kempinski, Four Seasons Hotel-Sultanahmet, Four Seasons Hotel at Bosphorus, Les Ottoman, W Otel, The Ritz-Carlton, Pera Palace Hotel-Jumeirah, Swissotel the Bosphorus, Hilton İstanbul, Divan Hotel, InterContinental Istanbul, Park Hyatt İstanbul-Maçka Palas, The İstanbul Edition, Radisson Blue Bosphorus, Witt İstanbul Hotel, Tomtom Suites, Bebek Hotel, A'jia Hotel, Eresin Crown Hotel Sultanahmet, Rixos Pera Istanbul, Sumahan on the Water, and so on. For those looking for mid-level accommodation, the Osmanhan Otel, Muyan Suites or the Dersaadet Hotel are good options. For those on more of a tight budget, the Basileus Otel, Şebnem Hotel or Serene Hotel are probably more what you're looking for. In and around Taksim and Sultanahmet are many cheap hostels, pensions, and inns.
Things you have to see when in Istanbul include the Historic Peninsula, which is a UNESCO World Heritage site, Topkapi Palace, Hagia Sophia, the Archeological Museum, The Blue Mosque, Süleymaniye Mosque, the Hippodrome, and Sultanahmet Square, The Museum of Turkish and Islamic Arts, The Basilica Cistern, Binbirdirek Cistern, the Grand Bazaar, Rüstem Paşa Mosque, Small Hagia Sophia, Chora Church, Eyüp Sultan Mosque, Fatih Mosque and Complex, the Theotokos Pammakaristos Monastery, the Land Walls and Tefkur Palace, the Spice Bazaar, New Mosque, the Golden Horn and all its surrounding historic neighborhoods, Galata Bridge, Galata Tower, Galata Whirling Dervish Hall, Istiklal Avenue, Taksim and its surroundings, Nişantaşı, the Maiden's Tower, Dolmabahçe Palace, Çırağan Palace, Yıldız Park and Palace, Ortaköy Mosque, Rumeli Fortress, the neighborhoods on the Bosphorus their stately mansions, Kadıköy and the Princes Islands. Some other fantastic sights include Divan Road, Beyazit Square and Beyazit Mosque, Yedikule dungeons, Sokullu Mehmet Paşa Mosque, the Fener Greek Orthodox Patriarchate, Pierre Loti Hill, Sirkeci and Haydarpaşa train stations, Mihrimah Sultan Mosque, Çorlulu Ali Paşa Mesrasah, the Aqueduct of Valens, Beylerbeyi Palace and Turkey's famous miniature models of some of its most famous architectural works in Minitaurk Park. Finally, Istanbul Modern, Santral Istanbul, Rahmi M. Koç Museum, Sakıp Sabancı Museum, the Mosaic Museum, Pera Museum, the Military Museum and the Museum of Innocence are all amongst the unique museums to be found in the city.
Istanbul isn't for nothing a city that greets tourists interested exclusively in shopping! There is an absolute wealth of historic bazaars, local bazaars, boutiques, shops and modern shopping centers. The Grand Bazaar alone has over 4,000 stores. From gems to carpets, from antiques to leather, from clothing to gifts - you can find everything you'd ever want in this totally original shopping paradise. Tourists typically come to look at local products like carpets, kilims, chalcedony (onyx stone), towels, loincloths, evil-eye beads, Turkish coffeepots, coffee cups, Turkish coffee, Turkish delight and teas. The Spice Bazaar in Eminönü is not just for spices, it's one of the places one just has to visit to get a sense of Eastern mysticism. On the European side, Istiklal and Rumeli avenues are the main shopping streets, and on the Asian side Baghdad and Bahirye avenues are both beautiful and the primary shopping avenues. Visitors should feel free to visit the boutiques and shops of Taksim, Nişantaşı, Osmanbey, Kadıköy, Beşiktaş and Bakırköy, or just go to the malls dotted all over the city. Istinye Park, Cevahir, Akmerkez, Kanyon, Profilo, MetroCity, Galleria, Marmara Forum and Capitol are some of the most popular malls in the city. There are also more than 200 local bazaars all over the city.
Istanbul is a 24 hour city that has something for everyone. You can get lost in its streets, or in its mystical bazaars, or catch a show at the Galata Whirling Dervish Hall, or take a short tour of Turkey in the Miniaturk Park. Or take a ferry out on the Bosphorus, or out on the Golden Horn or to the Princes Islands. Or you can look out over the lovely skyline of the city from the beautiful hilltops of Çamlıca, Nakkaş, Ulus Park, and Pierre Loti, or from the uppermost points of buildings like the Galata Tower or Istanbul Sapphire. Take a trip to the Maiden's Tower to drink some coffee and get a traditional Turkish massage in the historical bath house. Other typical activities you should make sure you do at some point in your visit include eating fish sandwiches in Eminönü, or eating the famous yoghurt made in Kanlıca, or eating mussels at Anadolu Kavağı, or smoking the hookah at Tophane or Çorlulu Ali Paşa Madrasah, or feeding the birds traditional Turkish breads from a ferry or in front of New Mosque. Those traveling with children should visit the aquarium, the Dolphinarium, the Toy Museum and any of the amusement parks inside of the major malls of the city. Football is the most popular sport in Turkey. For those visitors who are interested in football going to a derby between one of the three biggest clubs (Galatasaray, Fenerbahce, or Besiktas) can be quite an experience, particularly because of the unique passion shown by the Turkish supporters. For the Istanbul Eurasia Marathon the Bosphorus Bridge is opened to pedestrians just once a year, if you're looking for events to make the special trip for. There are many cultural events in Istanbul (like the International Art and Culture Festival, International Theater Festival, Istanbul Film Festival, International Istanbul Biennial, Music Festival and the Jazz Festival). In the summers, the Harbiye Open Air Theater puts on quite a large number of concerts. The Cemal Reşit Rey concert hall has many different musical and dance performances throughout the year. During the month of Ramadan and other religious holidays there are special activities associated with the specific holiday. The heart of Istanbul's night life is Taksim/Beyoğlu. On and right off Istiklal Street there are hundreds of bars featuring every kind of music you can think of.