As a solo traveler, I usually do my own research and plot a city walk tour that works for me.
In the past, I've used an app called "GPS My City". It has worked okay and I've paid for the full annual subscription in the past so I could edit and have custom walks. My subscription if up for renewal but I want to explore other options before committing again. They do have a free version that is basic with standard routes mapped out, but I like to customize them to my liking.
I've seen RS Audio tour mentioned here as well. I am exploring new apps for city walk tours that provides both map and a little description in written format (not audio). When exploring a city, I like to hear the sounds of the place and not have earphones on all the time.
Has anyone used any phone apps with guided maps during your travels? Or do you just pin on your map places you want to visit and follow directions there?