Panama city is a unique blend of tradition and modernism.  The contrast from the old city to the view of the bay skyline with it's high rises is quite fascinating.

 The city has a population of about 450,000 - about the same as Portland, Oregon - and the energy  of about the same as a combination of Rio de Janeiro, San Francisco, Rome, and Macao.  Definitely, don't miss absorbing all the atmosphere possible.
You just can't  miss the Panama Canal.  Tour agencies offer he tour which can take up to two and a half hours.  It is righteously recognized as the Eighth Wonder of the World.  A visit to the Panama Canal will unveil far more than an unprecedented engineering feat.  The Canal's watershed features abundant and record - setting wildlife.  Superb hiking and bird watching tours, and only minutes from downtown Panama City. 

Make sure you visit the world's most researched rain forest: the Smithsonian Institution's natural laboratory of Barrio Colorado Island in Lake Gatun. 

There is also an excellent shopping area on Via Espana in what is known as the "Hotel and Banking Area".   If you go in the other direction several miles on Via Espana, you have vendors lined up on the sidewalk selling everything from soup to nuts.