This is a cool little technique as learned from the wonderful Milliande. She is an amazing artist located in England, though her accent suggests her origins are elsewhere. Check out her Ning site right here. She also has some amazing You tube movies.
Grid journaling is great if you don't want to commit to sketching out one large picture. I love the idea of little snippets of buildings, fences and such. Here is one page filled with historic Sydney buildings, the Opera House and Sydney Harbour Bridge