Last summer I took the plunge and invested in a Herschel Backpack (similar one here). The medium style I picked up is just perfect for city breaks as well as for an in-flight carry-on. It's a really perfect size and even has a little pouch that fits my laptop in it perfectly. So here is a little look at the essentials I pack in there to go away.
Of course the most important thing is my passport as I wouldn't be getting very far without that! It's also handy when you're out and about as you never know when you might need a form of ID.
I rarely take my laptop away with me but I always bring my iPad on holiday. Whether it's to use Google Maps, browse at the airport or just to watch films during the journey, it's always handy to have. I can do most of the minimal things I need to whilst away and it's really compact.
Also for entertainment purposes, I have a cheap set of earphones. They're less valuable and bulky than my headphones so I can just slip them into my bag without worrying about it so if I'm travelling or go for a day at the beach I can easily have a bit of music.
It's also nice to have a point-and-shoot camera in there as it's much less bulky and easier to use on the go than my bridge camera. Also, it's less valuable. Whilst I'd be gutted to lose my camera abroad for all the photos on it, it would sting a lot less if I also wasn't losing £300+ worth of kit along with it!
Another essential is my Kindle. Especially on a beach holiday I tend to read a lot and it's so much more convenient than heaving along several print books with me. Also I can simply download another book onto it by Wi-Fi if I need to.
A guidebook is always good to have as you can't just expect every street to have internet access and data roaming charges can be huge. I also just like sitting in a cafe over breakfast with an old-fashioned guidebook and a pen and notebook to plan what we're going to do for the day.
A pair of sunglasses is also a must! I have a pair of folding Rayban Wayfarers which are fitted with my prescription. Another sun-protector is sunscreen; you never know when you might need a top-up so it's best to keep some on you. Also a nice, hydrating SPF lip balm. Another essential toiletry is tissues as especially at beaches the toilet can be a hole in the ground! For similar reasons but also just because you eat out so much on holiday anti-bacterial hand gel is something I always have with me. Finally I have painkillers, which to be honest even at home I always have in my bag as the last thing you want is a headache or stomach cramps ruining your day!
I tend to keep my valuables in a little bumbag. My friends find this hilarious but I've never been pick-pocketed abroad with this *touches wood*! I keep my currency, keys or key card and phone around my waist so I can always see it. Especially if you're going to be on a crowded Metro a lot you might not want to keep valuable items on your back. Saying that the one I have is really secure and has about 3 barriers you'd have to get through in order to get to the good stuff!