To the untrained eye, this is just another nondescript, white building at the V&A Waterfront in Cape Town. I walked past this building several times myself before I noticed the small board outside the entrance, that revealed the location's significance. Everyone traveling to and from Robben Island during apartheid passed through this building. For the prisoners, staff, and wardens, this was the last place they would see in Cape Town before watching the waterfront disappear into Table Mountain's dark silhouette, as the distance between their ferry and the mainland increased.
It's now a small museum, and you will find information about the full history of Robben Island, before and after apartheid. You can sit inside a replica of a holding cell, and an audio track plays to enhance the experience. It is typically not very crowded at this museum, giving you ample time to explore at your own pace.
Jetty 1 is separate from the Robben Island Exhibition and Information Centre, and is just past the V&A shopping mall. It's a must-see if you don't have a half-day to dedicate to the full Robben Island tour, but are curious about this part of Cape Town's history. It's also entirely indoors, so if you're visiting in winter and the weather isn't nice enough to visit Robben Island, this is the next best thing. Entrance is free.