Derince

Derince railway station (Turkish: Derince istasyonu) is a railway station in Hereke, Turkey. TCDD Taşımacılık operates four daily regional trains between Istanbul and Adapazarı that stop at the station. The station was originally built in 1904 by the Ottoman Anatolian Railway along with the Port of Derince.Derince station was closed down on 1 February 2012 due to construction of the Ankara-Istanbul high-speed railway. The station was reopened on 4 August 2017.

İzmit İsmetpaşa Stadium (Turkish: İzmit İsmetpaşa Stadyumu) was a multi-purpose stadium in the Derince district of İzmit in Kocaeli Province, Turkey. It was named after the Turkish general and statesman İsmet İnönü (1884–1973), widely known as İsmet Pasha. Built in 1972, it was situated on the Istanbul-İzmit highway D.100. The stadium held 15,462 spectators, and was primarily used for football matches as the home stadium of Kocaelispor.

USS PC-1640 was an PC-1638-class submarine chaser in the United States Navy during the Cold War. She was transferred to the Turkish Navy as TCG Yarhisar (P 113) of the Hisar-class patrol boat.

Gölcük Barbaros Hayrettin High School (Turkish: Gölcük Barbaros Hayrettin Lisesi), is a public high school in Gölcük, Kocaeli, Turkey. The school is named after Ottoman admiral Hayreddin Barbarossa. Short form of the school name is GBHL. Formed in 1958 as "Gölcük Lisesi" (GL), the high school named as "Barbaros Hayrettin Lisesi" in 1970 when it moved to its own building from the provisional location. The colors of the school are black (symbolizing the deadly ferry accident on 1 March 1958 in which hundreds of high school students died in Gulf of İzmit) and yellow (symbolizing the sun/GBHL rising after this disaster). In the devastating earthquake epicentered in Gölcük on 17 August 1999, GBHL lost many of its students and faculty residing in Gölcük and surrounding towns. The buildings of the high school has been damaged, however later been repaired by the efforts of its alumni association and some international relief organizations.

Gölcük, formerly known as Diolkides, is a municipality and district of Kocaeli Province, Turkey. Its area is 217 km2, and its population is 175,940 (2022). The city is located at the northern gulf of Armutlu Peninsula on the coast of Gulf of İzmit, a branch of the Sea of Marmara, in the south of the province. It is the district, where the 1999 earthquake disaster happened. Gölcük is the location of one of the Turkish Navy's main naval bases, and of a Ford Otosan automobile plant. The mayor is Ali Yıldırım Sezer (AKP).

Gölcük Naval Base (Turkish: Gölcük Deniz Ana Üssü) is the main base of the Turkish Navy on the east coast of the Sea of Marmara in Gölcük, Kocaeli. It is the principal base for logistic support with various facilities stretched over 1,800 acres (7.3 km2) of land. In addition to the workplaces, the base houses apartment-like barracks, social facilities, a military hospital, a military museum and an archive for naval history. The shipyard at the base is capable of constructing frigates, submarines, fast attack boats and auxiliary vessels with high technology in recognized standards.

Gölcük Naval Shipyard (Turkish: Gölcük Donanma Tersanesi) is a naval shipyard of the Turkish Navy within the Gölcük Naval Base on the east coast of the Sea of Marmara in Gölcük, Kocaeli. Established in 1926, the shipyard serves for the building and the maintenance of military vessels. A total of 3,221 personnel are employed at the shipyard stretching over an area of 255,526 m2 (2,750,460 sq ft) with covered structures of 121,466 m2 (1,307,450 sq ft).

Elaea or Elaia (Ancient Greek: Ελαία) was a town of ancient Bithynia on the coast of the Sinus Astacenus in the Propontis. Its site is located near Zeytin Burnu (Körfez), in Asiatic Turkey.

İzmit Körfez Circuit (Turkish: İzmit Körfez Yarış Pisti) is a motor sports race track about 17 km (11 mi) west of İzmit, in Körfez district of Kocaeli Province, Turkey. Sponsored by the Turkish Automobile Sports Federation (TOSFED) and built by the Istanbul Motorsports Club (İMK), it was inaugurated in 1993 as the first asphalted race track in Turkey. The venue is home to motor sport races in various categories. Located at the northeastern coast of Marmara Sea, İzmit Körfez Circuit is situated around a small Fener Lake (Fenergölü), which belongs to the Municipality of Körfez District. The venue can be easily reached from Istanbul and İzmit by the motorway O-4 or highway D-100 at the exit Körfez. The race track, 1.950 km (1.212 mi) at length, has nine turns and runs clockwise. The circuit provides the greatest number of motor sport racing events in Turkey. In addition to Turkish championships, several racing organizations of private companies as well as various motor sport types in different categories are held here. On an average racing day, several events are carried out in five to six categories. The circuit is used also for test runs by motor magazines, tire and motor companies. Some motorcycle and auto racing schools train here also. Around 5,000 spectators in every age group come to the circuit on racing days. Events at the race track find growing interest in the TV and press.

The 1999 İzmit earthquake (also known as the 17 August Earthquake or the 1999 Gölcük Earthquake) was a magnitude 7.6 earthquake which the Kocaeli Province of Turkey on 17 August 1999. Between 17,127 and 18,373 people died as a result, and it caused an estimated US $6.5 billion in damage. It was named for the quake's proximity to the northwestern city of İzmit. The earthquake occurred at 03:01 local time (00:01 UTC) at a shallow depth of 15 km. A maximum Mercalli intensity of X (Extreme) was observed. The earthquake lasted for 37 seconds, causing seismic damage, and is widely remembered as one of the deadliest natural disasters in modern Turkish history. The 1999 earthquake was part of a seismic sequence along the North Anatolian Fault that started in 1939, causing large earthquakes that moved progressively from east to west over a period of 60 years. The earthquake encouraged the establishment of a so-called earthquake tax aimed at providing assistance to those affected by the earthquake.

Ford Otomotiv Sanayi A.Ş. (Turkish for 'Ford Automotive Industry'), doing business as Ford Otosan, is an automotive manufacturing company based in Turkey that is equally owned by Ford Motor Company and Koç Holding. The company was established in its current form in 1977, with original relations dating back to 1928. It currently operates in six locations: Gölcük and Yeniköy plants in Kocaeli, İnönü plant in Eskişehir, Craiova plant in Romania, Sancaktepe R&D Center and spare parts warehouse in Istanbul The company employs more than 20,000 people and had a production capacity of over 700,000 vehicles, 400,000 engines, and 140,000 powertrains by 2022.

Diolkides was a town of ancient Bithynia. Its site is located opposite Zeytin Burnu, Gölcük, in Asiatic Turkey.