All of the locations listed are associated with San Juan, Puerto Rico. However, if we consider their specific context:
- Plaza las Américas is a large shopping mall in San Juan.
- Museo de las Américas is a museum located in Old San Juan.
- San Felipe del Morro is a historic fort located in San Juan.
On the other hand, Mercado Modelo is a market that used to be located in San Juan but has since been relocated or is less commonly associated with San Juan in recent times.
If the question is about which of these is not a prominent or widely recognized site as of my last update, Mercado Modelo might be the best answer.
Please always check current sources for context, as things may have changed.