Fuerte Amador (Balboa), Panama, is the port closest to the Pacific entrance of the Panama Canal. It's a district of Panama City, located at the entry point to the canal; cruise ships anchor out in the ocean and tender passengers to offshore islands, across a causeway from the city.
The main attraction here is, of course, the Panama Canal, which ships are either just exiting or about to enter. Tours take cruise passengers to the Miraflores Locks or on boat rides through the canal's Gatun Lake. Other tours focus on attractions within Panama City, such as the Frank Gehry-inspired Biomuseum or walking tours through the heart of the city.
If you're planning on touring independently, know that Panama City has fairly bad traffic and getting from the tender pier to and from town may take longer than you expect.