Black Star Square
The independence parade ground, and the arch you have seen in every photograph of Accra.
Independence Square, with the Black Star Gate at one end and the sea at the other. It is a parade ground rather than a park, so there is not a great deal to do beyond walk it and photograph it, but it is the image of Accra and it takes twenty minutes.
It sits next to Osu Castle and a short drive from Jamestown, so it slots into a morning rather than needing one.