I think Forest Park is the largest urban park in the US. If he is alone, or with family, it is a great place to spend the day including golf or not. The zoo and art museums are contiguous and free. I recommend a quick trip to the Penguin House and then a short walk up the hill to view the collection of George Caleb Bingham paintings on the first floor of the museum. Jolly Flatboatmen in Port will leave a smile on your friends face for the duration of his trip. While neither the course, museum or zoo stands on its own for a given detour, the three together make a can't miss opportunity.