San Juan is the capital of the state of Puerto Rico.
Puerto Rico was particularly interesting for the "conquerors" - whether Spanish or English - because of its strategic location in the Caribbean.
Finally, I was able to take a closer look at San Juan and Puerto Rico from the air. There are already plenty of pictures from the ground:
Puerto Rico Pictures.
San Juan is full of history and very well preserved - in addition to the old town, the fortresses 'Castillo San Felipe del Morro' and 'Castillo de San Cristóbal' are particularly worth seeing.