This is a good shot of el Morro as we have passed it on our way to the cruise ship pier. If you are ever in San Juan, you must make the trip to this fortress. The best was is to take a taxi or ride the free trolley out there. There is a bit of a walk from the front to the actual entrance. It is up on a hill, so returning one can walk downhill the rest of the way back. As I recall from my last visit, the guide related that this fortress has never been breached. Once you get to the top of one of the outer walls, you will understand why that is.

In the lower portion of the picture you can see some of the walls that surrounded the city, all set up with a goal of defense of the city. It is impressive.

I believe that this is the US Customs House, but cannot verify that information.
Puerto Rico is a territory of the United States, and the residents are US citizens, although they have no voting rights in the general elections of the US. The currency is US dollars. English is spoken, but Spanish is the primary language.
Puerto Rico was claimed for Spain by Christopher Columbus on his second voyage. Many ships came there looking for whatever they could find of value to take back to the homeland. Those ships used bricks as ballast and those were left and replaced with loot. Those bricks make up many of the street paving in Old San Juan.
Many cruise lines begin and end their itineraries in San Juan, mostly on Saturdays and Sundays. As a result their airport can be extremely busy on the weekends. Other cruises call at San Juan as part of an itinerary that sails from Florida; often the timing on those is less than wonderful, as you might arrive in mid-afternoon and depart late at night. Shopping is minimal after sundown, so a trip to the casino is one of the primary options. If you have San Juan as a port of call, check out the arrival and departure times.
Because there are so many cruise ships arriving there, San Juan has many piers, most of them within an easy walk to the many part of San Juan. There are a couple much farther out and a taxi might be more practical to get into the center of the action.

This is the pier where we will be. As you can see, we will be right in town. I can recall from the 1980s there were plentiful shops for souvenirs; and now there are more.

There are restrictions on the style of architecture that is allowed for any new or remodeled buildings. Old San Juan is a tourist city whereas the new San Juan is the city that many would expect in a modern society as far as architecture.

It looks so peaceful and quiet in your pictures, but I suppose this is a very busy port if tourism is the major industry

We were there on a Monday, having sailed from Ft. Lauderdale on a Friday. Most cruises with begin/end on the weekend. Of, if they are leaving from Miami or Ft. Lauderdale, they would not be in San Juan until later in the week.

The San Juan harbor is ideally suited for cruise ships because of the configuration of the harbor. The entrance, on the north side of the island, keeps most waves and stuff out of the scene. As you can see, there isn't much wave action in the early morning (6:00 a.m.). By afternoon, during the heat of the day, the wind will increase and it can be choppy in the open water.

What really surprised me how empty it looked. I would have thought that there would be more traffic, if not of big ships, at least small or fishing boats.
Your narration and pictures are so enjoyable