Some weeks from now, or even years later, these notes will be a gold mine for a fiction project. When you want to write a scene set in a cave, a children's playground, a castle ruin or a pub, you can look up your notes and create authentic, original setting descriptions. These will be far more vivid than what you can create from your imagination or memory.
Take this book with you on your journeys and holidays, and to all the places you've never been before. Fill in a section whenever you have time to kill, for example in the laundrette, at the bus stop, or in the doctor's waiting room.
You can also establish a daily or weekly writing ritual, regularly completing a section about a different place. Soon you'll have a wealth of material to draw from.