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Miley Cyrus, Patrick Schwarzenegger

Splash News

Wild child Miley Cyrus celebrated her 22nd birthday in true Miley style.

The pop star celebrated with new boyfriend Patrick Schwarzenegger, 21, and several friends at a new Beacher's Madhouse secret location by the Santa Monica Pier, where she was presented with an enormous pizza cake and rode a mechanical ride in the form of a penis (see the NSFW pic here).

Miley, who had used giant inflatable phalluses on stage during her Bangerz tour concerts, arrived at her party in a colorful outfit, consisting of a bright pink top that connected with a ring to her fluorescent green mini skirt, covered with a pink and yellow fur jacket. She sported blue eye shadow, blue and yellow hearts painted on her face and pink and blue butterfly clips in her short hair.

She was photographed near the Factory Club with Patrick (dressed in an olive green flight suit), her brother Braison Cyrus, 20 (dressed in plaid), and friends. Singer and actress Sky Ferreria also attended the party, E! News has learned.

Cyrus posted a photo on Instagram of her pizza cake.

"It's my buuuurffffdayyyy," she said.

A photo posted by Miley Cyrus (@mileycyrus) on

Her friend Katy Weaver, who also attended the party, shared another pic.

Pizza cake!!!!!!!!!!!!

Una foto publicada por Katy Weaver (@katyweaver) el

"Everyone had a great time," a source told E! News. "It was a fun and relaxed and it was quite a spectacle. Nothing less than what you would expect from a party with Miley."

PHOTO: Miley Cyrus and Patrick Schwarzenegger pack on the PDA

Patrick is the eldest son of Arnold Schwarzenegger and Maria Shriver, who share four children. E! News learned about his and Miley's relationship in early November. Several sources said they were "casually dating."

Since then, Patrick and Miley have been spotted out together several times this month, including at a USC football game, where they packed on the PDA, and during several dates.

This is the most high-profile relationship for Miley since she and actor Liam Hemsworth, her co-star in the 2010 movie The Last Song, ended their engagement and broke up in September 2013.

"I have seen Miley with Liam and other boyfriends but honestly I have never seen her look as loved up as this," an insider told E! News last week. "This is more than just a fling, they look like they are falling in love with one another."

—Reporting by Baker Machado