Anna Kournikova & Enrique Iglesia engagement ring

The Russian tennis star has kept her relationship with musician Enrique Iglesias under wraps since the early 2000s. Her engagement ring, though, is difficult to overlook.

Anna Kournikova was given an 11-carat champagne and cognac pear-shaped diamond ring in 2004 that was reported to be worth between $2.5 million and $6 million (between £2.5 million and £6 million in today's money). The pink-colored center gem is surrounded by trillion-cut diamonds from the Argyle mines in Western Australia.

Her now-husband, who is known for his love ballads, also gave Kournikova a $5.4 million (about £4 million) radiant-cut canary yellow diamond, which has been seen on her finger during tennis matches.

The yellow-colored Anna Kournikova & Enrique Iglesia's engagement ring is now valued at about $7.5 million (£5.4 million), making it one of the world's three most expensive engagement rings.

Estimated Cost : $7.5 million