Question: the winners of the 1998-99 Argentine football league championships were based in this city?

Context paragraphs:
1891 in Argentine football: 1891 in Argentine football saw the first ever Argentine championship which was run by the Association Argentine Football (AAF) making Argentina's the oldest football league outside mainland Britain.  This tournament was organized by the Argentine Association Football League which president was F.L. Wooley.  This league only lasted one season, so in 1892 no championship was held.  In 1893 other Association with the same name would be established by Alexander Watson Hutton becoming current Argentine Football Association.

Víctor Valussi: Víctor Miguel Valussi (8 May 1912 - 1 April 1995) was an Argentine football defender who won four league championships with Boca Juniors and played for the Argentina national team.

Boca Juniors: Club Atlético Boca Juniors (] ) is an Argentine sports club based in the La Boca neighbourhood of Buenos Aires.  Although many activities are hosted by the club, Boca Juniors is mostly known for its professional football team which, since it was promoted in 1913, has always played in the Argentine Primera División, becoming the most successful team of Argentina in number of official titles, with 66 won to date.  National titles won by Boca Juniors include 32 Primera División championships, and 12 domestic cups.  Boca Juniors also owns an honorary title awarded by the Argentine Football Association for their successful tour of Europe in 1925.

Carmelo Simeone: Carmelo "Cholo" Simeone, (22 September 1934 – 11 October 2014) was an Argentine football defender who won three league championships with Boca Juniors and played for the Argentina national team.  Nicknamed "Cholo", he was known for his energetic playing style.

Antonio Alberino: Antonio Américo Alberino (born 26 October 1910, date of death unknown) was an Argentine football striker who won two league championships with Boca Juniors.

1998–99 in Argentine football: In 1998-1999 Boca Juniors were the winners of both league championships in Argentine football.

Juan Yustrich: Juan Elías Yustrich (9 July 1909 - 6 October 2002) was an Argentine football goalkeeper who won two league championships with Boca Juniors.

1999–2000 in Argentine football: The 1999-2000 season in Argentine football saw River Plate win both the league championships, while Boca Juniors won the Copa Libertadores 2000 and Talleres de Córdoba won the 1999 Copa CONMEBOL to become the first team from Córdoba Province to win a major international title.

1998–99 Primera B Nacional: The 1998-99 Argentine Primera B Nacional was the 13º season of second division professional of football in Argentina.  A total of 33 teams competed; the champion and runner-up were promoted to Argentine Primera División.

Pedro Dellacha: Pedro Rodolfo Dellacha (9 July 1926, Lanús – 31 July 2010) was an Argentine football defender and coach.  He was the captain of the Argentina national team that won the 1957 Copa América and earned the nickname "Don Pedro del Area".  As a manager, he won the Copa Libertadores twice and league championships in four countries.

Supporting paragraphs: 1998–99 in Argentine football Boca Juniors
Answer: Buenos Aires