1961, John had gotten £100 in birthday money. What did he use it on? A holiday (or vacation) He could've gone with Cynthia - who we'll get to in a little while. But John intended on hitchhiking to Spain with none other than... Paul! They didn't get to Spain but they did manage to get as far as Paris. In the anthology Paul said.
"Anyway, one of John's relatives gave him £100 I would be impressed. And I was his mate, enough said? 'Let's go on holiday.' 'You mean me too? With the hundred quid? Great! I'm part of this windfall.'
Paul and John got turned down, and Paul (who had hitchiked with George) knew they needed a gimmick so the pair bought bowler hats. They were already wearing their leather jackets and drainpipe jeans.
"We'd never been there before. We were a bit tired so we checked into a little hotel for the night, intending to go off hitchhiking the next morning. Of course, it was too nice a bed after having hitched so we said, 'We'll stay a little longer,' then we thought, 'God, Spain is a long way, and we'd have to work to get down there.' We ended up staying the week in Paris – John was funding it all with his hundred quid."
John actually celebrated his 21st birthday in Paris and off Paul he got a hamburger. Paul said that John was "Must have been fond of me to spend that money. He let me have all the banana milkshakes I wanted."

John said
'I first went to Paris aged about twenty-one – well, actually I was twenty-one in Paris, but. The thing was all the kissing and the holding that was going on in Paris. And it was so romantic, just to be there and see them, even though I was twenty-one and sort of not romantic. But I really loved it, the way the people would just stand under a tree kissing; and they weren't mauling at each other, they were just kissing'

It was also in Paris where the two got the 'Beatle' haircut.
They took a few photos on the trip but my favourite would be

It's of John sleeping and apparently Paul has it framed in his house.