Question: In which county was Ira Rennert's mansion constructed ?

Context articles: Sagaponack, New York
Renco Group
Otsego Lake (New York)
Ari Rennert
Alexander Ljungqvist
Emma Flower Taylor Mansion
Yalı
Upton (Baltimore, Maryland)
Hillsborough House
The House that Ate the Hamptons

Sagaponack is a village in the Town of Southampton in Suffolk County, New York, United States, on the East End of Long Island.
 The village was incorporated on September 2, 2005.
Renco Group is a New York City-based holding company controlled by Ira Rennert that invests in other companies across a range of industries.
Otsego Lake is a 4046 acre lake located in Otsego County, New York and is the source of the Susquehanna River.
 The Village of Cooperstown is located at the lake's southern end.
 Glimmerglass State Park is located on the lake's northeastern shore, and includes Hyde Hall, a large mansion constructed in 1817 that overlooks the lake.
 Glimmerglass Opera is located on the western shore.
Ari Rennert is an American businessman, the president of Renco Group, a private holding company founded in 1975 by his father, Ira Rennert.
Alexander Ljungqvist is a Swedish economist, educator, researcher, writer, and speaker.
 He is a professor of finance at New York University Stern School of Business where he holds the Ira Rennert chair of finance and entrepreneurship.
 His areas of expertise include corporate finance, investment banking, initial public offerings, entrepreneurial finance, private equity, venture capital, corporate governance, and asset pricing.
 Professor Ljungqvist teaches MBA and executive courses in private equity and venture capital and a PhD course in corporate finance.
Emma Flower Taylor Mansion is a historic home located at Watertown in Jefferson County, New York.
 It was built in 1896–1897 and is a massive 2 ⁄ -story mansion constructed of rock faced, random course Medina sandstone which was hand-cut on site.
 The footprint is 5628 sqft , not including the porches and porte cochere.
 It is Queen Anne in style and features wraparound porches, towers, projecting bays, dormers, and a complex roofline.
 It was constructed as a wedding gift to his daughter by New York Governor Roswell Pettibone Flower.
A yalı (Turkish: "yalı" , from Greek γιαλή "yialí" (mod.
 γιαλός "yialós"), literally "seashore, beach") is a house or mansion constructed at immediate waterside (almost exclusively seaside, particularly on the Bosphorus strait in Istanbul) and usually built with an architectural concept that takes into account the characteristics of the coastal location.
 A family who owned a waterside residence would spend some time in this usually secondary residence located at the sea shore, as opposed to the "konak" ("mansion", aside from the term's use to refer to buildings with administrative functions) or the "köşk" ("pavilion", often serving a determined practical purpose, such as hunting, or implying a temporary nature).
 Thus, going to the "yalı" acquired the sense of both going to the seaside and to the house situated there.
 In its contemporary sense, the term "yalı" is used primarily to denote the total amount of 620 waterside residences, mostly dating from the 19th century (some of them date from the 18th century, and some from the early 20th century), sprinkled along the Bosphorus in Istanbul.
 As such, they constitute one of the city's landmarks.
Upton, also known as the David Stewart Residence or Dammann Mansion, is a historic home located at Baltimore, Maryland, United States.
 It is a large brick Greek Revival mansion constructed about 1838 as the country residence of David Stewart (1800-1858), a prominent Baltimore attorney and politician.
 It is 2 1/2 stories high on a raised basement, three bays wide and two rooms deep, with a center-passage plan.
 In the late 1950s, a brick stair tower was constructed when the building was adapted for public school use.
Hillsborough House, later called Hillsborough Hall, is a large, stone-built mansion constructed in the Adam style in the latter part of the 18th century.
 It stands 2½ miles north-west of the centre of Sheffield at grid reference [ SK331901] in the suburb of Hillsborough within Hillsborough Park, a council-owned public recreational area.
 For 124 years the house was a private dwelling, but since 1906 it has housed the Hillsborough branch library.
 It is a Grade II listed building as are the coach house and stables which stand 20 m north west of the main house.
The House That Ate The Hamptons is a novel based on the controversy surrounding the construction of billionaire Ira Rennert's mansion in Sagaponack, New York.