I can't find this info nor can I even figure out how to phrase the problem well. Sorry.

Say I'm in Paris, which I don't know well. Some nice person takes me home for the night; I walk outside the following morning and I promise my new friend that I'll come back at the end of the day. I wander all over the city, and in the evening I want to get back there.

Assuming I had previously downloaded maps of Paris, is there something I could have done in the morning when I left my friend's house -- create a custom POI or a Waypoint or what? -- such that, in the evening, even without internet access, I could find that spot on my map and see where it is compared to my current GPS-indicated location? How, in the evening, do I look up the point that I took a reading on in the morning? (I'm not talking about having a route laid out, which I know requires internet access; I just want to be able to use MM to show me where on the map my friend's house is.)

Or, say I go for a day-hike in a huge park. I have pre-loaded great satellite maps of the park. I park my car somewhere around the perimeter of the park. While I'm standing next to my car, I do something (but I don't know what) in Maemo-Mapper with my N810 and its GPS function. Then I wander all over the park. Later in the day, I want to find my car. What should I have done with Maemo-Mapper when I first got out of my car, and then what do I do when I want to find my car at the end of the day?