The current Acropolis is the consequence of hundreds of years of building and destroying. Most of the construction dates back to the 5th century BCE, although others, including a Roman-era temple built by Augustus and a massive stairway constructed by Claudius, were added later.
During the Ottoman Empire's control, small homes were also built in the area around the Acropolis. You will have the best experience if you walk there through Athens. If you have only one day in Athens, walking will allow you to explore other archaeological sites on your way. Considering your available time, you can explore other sites as well.