Martoni's Italian Restaurant at 1523 Cahuenga Blvd in Hollywood, California, opened in 1960 and quickly became a favorite of Hollywood's elite, especially musicians.
In "When Harry Met E. J." artist / writer / photographer / musician / ..., E. J. Gold, recalls having lunch with Harry Nilsson after Harry's audition for Rick Jarrard at RCA:
After the excitement following the audition had died down - it took a while, believe me, because nobody in the industry had ever heard anyone quite like Harry before - several of us, Harry among them, had lunch at Martoni's, hit it off great, were great friends thereafter, and still are.
When recording at nearby RCA Studios, Harry Nilsson would often visit Martoni's:
There was an Italian restaurant, Martoni's, very close to RCA and it would stay open late for us and we'd go and eat there and then they'd drink a couple of bottles of wine, and whatever else they were particularly liking that night. And then they'd go back to the recording session again. Total craziness. Those were pretty amazing nights. Actually Harry got into wine at that time, now I think about it. He used to drink some pretty expensive bottles of wine, some very nice wine!
-- Samantha Juste 
In his interview for the "One Last Touch of Nilsson" article (and Personal Best liner notes) Nilsson recalled running into Chip Douglas at Martoni's in 1967:
I said, 'Hi, Chip! What are you doing?' 'I'm producing these guys.' I said, 'I'm sorry, who are these guys?' He said, 'These are the Monkees.' I had heard all the publicity about them, but I didn't know what they looked like. I said, 'Oh, fantastic!' They were doing their first or second album. Chip said to the Monkees, "Harry is a fantastic writer. I would like to take him into the studio and let you hear a couple of tunes of his.' I said, 'Sure, I'd love to.' He said, 'Would you come over now?' I said, 'Yeah, I'd love it.' Especially because I'd heard rumors that they were going at four million record sales out of the box.
In his unpublished autobiography, Harry Nilsson recalls being picked up at Martoni's for his first meeting with George Harrison:
I was met by a car at Martoni's in Hollywood, transferred, and driven to a point in the Beverly Hills area. There I was transferred to another car, and to Blue Jay Way, where we passed the house, turned around and came back, to see if we were followed. I was ushered into this beautiful house with an open main room and a bar. To the right was a large back area with the pool, statuary and so forth.
Not knowing anyone and feeling very nervous and shaky about meeting a Beatle ... Derek Taylor took me by the hand and introduced me to his wonderful wife Joan, who was pregnant with Dominic at the time ... Derek took my elbow and led me outside. I was looking around wondering, "Where is the man?" Finally I saw him. He was standing at the far end of this long, narrow swimming pool in a white windblown robe with a beard and long hair, looking like Christ with a camcorder. So there he is!
Derek said, "George, I’d like you to meet the man."
He walked me over and said, "George, this is Harry. Harry Nilsson - George Harrison." George says, "Yeah, right, Harry. Can we get you something, a Coke, a coffee, or something?" He was looking me over and I thought, "Wow! He’s offering me something to eat or drink! This is amazing!"
-- Harry Nilsson
Radio personality ("professional rock and roll interviewer"), Doug Thompson, recalled moving to Los Angeles, California, in 1970, and visiting Martoni's:
During the many months that I popped in for a quick bite, I saw dozens of celebrities, including the legendary (and now infamous Phil Spector, whose usually haunt was Cantor’s Delicatessen on Fairfax, near Fairfax High where Phil went to school). I used to see Harry Nilsson practically every night, but he mainly frequented a bar on Sunset down the block called The Jolly Roger.
In a 1971 column in Cashbox, Ed Kelleher writes about seeing Nilsson, among many other celebrities, while dining at Martoni's:
A week before he left for Europe, the Jay Gatsby of rock, Harvey Geller, and I held one of our ritual rendezvous at Martoni's, where we eat salad, watch the front door, and generally do a turn as part of the music industry atmosphere that keeps Mario and Tony in pasta. Harv waved at Herb Eiseman. I waved at Nick Sevano, who was entering with Anne Murray, then we both waved at my cousin Sal, the bartender [...]
"Remember one thing," Harvey suggested, pausing between garbanzo beans. "It never hurts to put a lot of names in the column."
"I'll do that, Harv," I assured him, waving at Larry Van Nuys, who was waving at Harry Nilsson, who was waving at Grelun Landon, who was smiling at every-one and passing out 1971 Elvis pocket calendars. Steppenwolf, Three Dog Night and The Grass Roots walked in, taking bar space vacated seconds earlier by Chicago, Poco, Seatrain, Seals & Crofts, Joy of Cooking, Dawn, The Poppy Family, The Partridge Family and James Taylor, who was looking for his brothers and sisters.
"My guest column will be a symphony of proper nouns," I promised.
-- Ed Kelleher (1971) 
In 1983, Harry and his friend, Michael Macaluso, ran into Rob Reiner at Martoni's, They turned down Reiner's invitation to be a part of the audience for a concert he was filming for a rock movie.
Martoni's closed in 1994, shortly after the Northridge Earthquake (and, coincidently, Harry Nilsson's passing).