Much bigger aquarium than Sea Life, with over 1,500 species. 3 cafes and large parking lot.
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formerly San Stefano or Ayastefanos
A mostly upscale suburb on the coast of the Sea of Marmara, just south of the former airport. It was a multicultural village during the Ottoman period — the legacy of which still lives on in numerous churches of different Christian denominations dotting its streets — and later a seaside resort. Town centre has colourful wooden houses with highly decorative exteriors from the turn of the 20th century, especially around the railway station (itself a historic building) and the main street leading to it (which has many restaurants and cafes.) One mansion was where the Treaty of San Stefano was signed in 1878, ending the war with Russia — the frontline had extended this close to Constantinople. Town's main sights are the Aviation Museum and Istanbul Aquarium (not related to Sea Life). Get here on the Marmaray. Traffic in Yeşilköy is often congested, and parking is very hard to find.
Hava Kuvvetleri Müzesi
A military-based museum with various warplanes, helicopters, and weapons used by Turkish Air Force, and also civilian air transport and examples of Turkish aeronautics from Ottoman era onward.
little lagoon
This district lies between the "little lagoon" of that name, and Ataturk airport. It houses the Halkali Railway Station. There are lakeside areas for strolling and cycling, and there is a 16th-century stone arch bridge over the creek that connects the lake to the sea, but you wouldn't make a special trip.
Turkuazoo
Aquarium where you walk through transparent tunnels underwater. It's small compared to Istanbul Aquarium in Yeşilköy, an hour will be plenty, and their combi-tickets with Madame Tussauds (in Beyoğlu) and Legoland indicate their target audience.