Rocco Ritchie spent his 16th birthday inside a volcano.

The son of Madonna and Guy Ritchie, who was stuck in the middle of a custody battle earlier this year, travelled to the Thrihnukagigur volcano in Iceland with his step-mother Jacqui Ainsley to celebrate his big day.

Jacqui, 34, posted photographs taken from 120 metres inside the volcano on Instagram, saying it was a ''magical experience to journey into the Earth's womb''.

Allied to the volcano visit, Rocco was also gifted a Kabbalah protection bracelet by his famous father, which is supposed to keep him safe.

A source told the Sunday Mirror newspaper: ''Guy and Jacqui had a Kabbalah wedding and they wanted something based on belief and spirituality for Rocco's present.

''It's a silver and gold protection bracelet with his star sign birth stones, moonstone and topaz.''

Madonna, for her part, was recently filmed taking her son to get a piercing for his birthday.

The chart-topping pop star was seen taking Rocco to Elite Jewelry & Piercing in Manhattan, New York, last week.

Rocco is reported to have walked out of the venue with a stud in one of his ears.

He chose a gold square stud costing $120 for the earring and an additional $15 for the piercing, according to the gossip website TMZ.

Madonna also posted a series of heartfelt messages on Twitter to celebrate her son's birthday.

She wrote: ''Happy Birthday to my First Born Son! A true Warrior with a beautiful Heart. Let the Sun shine! (sic)''

She also said: ''Once my baby always my baby. Happy Sweet 16! (sic)''