You absolutely do not need to book in advance to visit the White Lighthouse of Dakar, Senegal. As of our visit they were requiring people to park at the bottom of the hill and take a shuttle to the top, but other than that slight delay you can go any time they're open. Only if you want to go as part of a longer city tour would you need to book in advance. There is also a restaurant next to the Phare des Mamelles where you can get a nice meal with an incredible view. Reservations weren't necessary when we visited.