Question: The Keçiören Bağlumspor is a team that is from the second largest city, behind what former imperial capital?

Context paragraphs:
Keçiören Bağlumspor (women's hockey): The Keçiören Bağlumspor is a Turkish women's field hockey side of Keçiören Bağlum SK based in Bağlum neighborhood of Keçiören district in Ankara, Turkey.  It is sponsored by the Keçiören Municipality.  The team plays in the Turkish Field Hockey Women's Super League (Turkish: "Türkiye Kadınlar Açık Alan Hokey Süper Ligi" ) and is coached by Mustafa Çakır.

Quảng Trị Province: Quảng Trị (] ) is a province on the North Central Coast region of Vietnam, north of the former imperial capital of Huế.

Huế Museum of Royal Fine Arts: The Huế Museum of Royal Fine Arts is a museum dedicated to Vietnam's imperial past and arts of that era.  It is located in the former imperial capital of Huế.

Imperial City, Huế: The Imperial City (Vietnamese: "Hoàng thành" ) is a walled palace within the citadel ("Kinh thành") of the city of Huế, the former imperial capital of Vietnam.

Dar El Menia: Dar El Menia is a Riad or Dar, a traditional Moroccan house built around a central courtyard and lies in the heart of Fez (Fes) Medina, former imperial capital of Morocco and the world’s largest medina.  Situated in this UNESCO World Heritage Site this dar, or courtyard house, was built in the 14th Century and has been recently extensively restored using local craftsmen, techniques and materials.  The house is now run as a guest house by an Englishman Graham Coules.

Hanoi: Hanoi ( or ; Vietnamese: "Hà Nội" , ] ) is the capital of the Socialist Republic of Vietnam and the country's second largest city by population.  Its population in 2009 was estimated at 2.6 million for urban districts and 7 million for the metropolitan jurisdiction.  The population in 2015 was estimated at 7.7 million people.  From 1010 until 1802, it was the most important political centre of Vietnam.  It was eclipsed by Huế, the imperial capital of Vietnam during the Nguyễn Dynasty (1802–1945), but Hanoi served as the capital of French Indochina from 1902 to 1954.  From 1954 to 1976, it was the capital of North Vietnam, and it became the capital of a reunified Vietnam in 1976, after the North's victory in the Vietnam War.

Ngô Đình Cẩn: Ngô Đình Cẩn (1911 – 9 May 1964) was a younger brother and confidant of South Vietnam's first president, Ngô Đình Diệm, and an important member of the Diệm government.  Diệm put Cẩn in charge of central Vietnam, stretching from Phan Thiết in the south to the border at the 17th parallel, with Cẩn ruling the region as a virtual dictator.  Based in the former imperial capital of Huế, Cẩn operated private armies and secret police that controlled the central region and earned himself a reputation as the most oppressive of the Ngô brothers.

Huế University: Huế University (Vietnamese: "Đại học Huế" ) is a university located in Huế, the former imperial capital of Vietnam; it is one of the important regional universities of Vietnam.  In Vietnam, universities are classified into three classes: national university (Vietnam National University, Ho Chi Minh City, Vietnam National University, Hanoi), regional university (Thái Nguyên University, The University of Da Nang and Hue University) and university.  Hue University is top 5 Vietnamese universities and top 350 universities in Asia according QS Ranking 2016.

John J. Tolson: John J. Tolson III was a Lieutenant General in the United States Army.  During the Vietnam War, he helped implement the airmobile concept use of helicopters in combat with the 1st Cavalry Division (Airmobile).  Tolson gives credit to the U.S Marines for first using helicopters to transport troops into combat in the Korean War, making the ground fight a three-dimensional war, thus freeing our troops from the tyranny of terrain.  Maj. Gen. Tolson took command of the division in April 1967 and served in that capacity till July 14, 1969.  During his command his division played crucial roles during the Tet Offensive at the former Imperial capital at Hue and at Quang Tri City in January 1968.  It also participated in the second biggest battle of the war: the relief of the Marine Khe Sanh Combat Base in March 1968 where all three brigades engaged the enemy, as well as the massive air assault into the A Shau Valley in April 1968 where the First and Third Brigades attacked the north end of the valley and leapfrogged south.

Ankara: Ankara (  ;  ] ), formerly known as Ancyra (Greek: Ἄγκυρα ) and Angora, is the capital of the Republic of Turkey.  With a population of 4,587,558 in the urban center and 5,150,072 in its province , it is Turkey's second largest city after former imperial capital Istanbul, having overtaken İzmir.  The former Metropolitan archbishopric remains a triple titular see (Latin, Armenian Catholic and Orthodox).

Supporting paragraphs: Keçiören Bağlumspor (women's hockey) Ankara
Answer: Istanbul