Looking back at some of my notes I am getting myself confused...

What is the difference between до + до and под + к when used with motion verbs? I find it difficult to differentiate and my textbooks don't do a very good job.

For example, I think the following mean..

Я подошел к остановке. I walked up to the stop.

Я дошел до конца квартала. I walked (up) to the end of the block.