Sao Paulo, Brazil ? Surrounded by palm trees and azalea bushes on a lush estate, Greek billionaire Athina Roussel Onassis is expected to say ‘I do’ to an Olympic athlete today in what Brazilians expect will be one of the most lavish weddings in years.

The 20-year-old Onassis – granddaughter and sole heiress of the late shipping tycoon Aristotle Onassis and one of the world’s richest women – will marry Brazilian equestrian star Alvaro Afonso de Miranda, the 32-year-old son of an insurance company owner.

Miranda, known popularly as Doda, was a member of the Brazilian showjumping team that won a bronze medal in the 1996 Atlanta Olympics and another in 2000 in Sydney, Australia.

The wedding was scheduled at the Maria Luiza and Oscar Americano Foundation, an 18.5-acre spread that includes a museum, a teahouse and a cultural center. The estate is in Sao Paulo’s upscale Morumbi district, near the palace where the governor of Sao Paulo state lives and works.

The couple, who share a love for horses and showjumping, met in 2002 at a riding center in Belgium owned by Brazilian equestrian Nelson Pessoa.

Athina Roussel Onassis was raised in Switzerland by her French-born father, Thierry Roussel. She inherited an estimated $2.7 billion from her grandfather on her 18th birthday. Roussel’s presence at the wedding hasn’t been confirmed.