There's a lot of German influence in the historic King William District. https://www.tripadvisor.com/Attraction_Revie…
The Handbook has a good article on German influences in Texas architecture, including why these are largely influences and mixing with American southern styles. Germans and people of the Germanic regions were the more sophisticated immigrants to Texas. (Before them, San Antonio was where Spain moved people from the Canary Islands to populate the colony.) They were often intellectuals fleeing prison or death threats at home on account of their political and social views. Castroville is Alsatian and is not far at all from San Antonio.
There's also an article here: https:/…Architecture.html
You will, of course, find other, later influences, as with anywhere. But Germans were also often the 19th century craftsmen here, so design and construction tended to exhibit what they knew.
Many of our courthouses (Texas has 254) are Romanesque Revival. It was the trend with courthouse designers of the time. Bexar County Courthouse is one.
This is the Otto Meerscheidt House, downtown SA. uncoveredtexas.com/images/…knwvlwtr.jpg
You'll probably find something like this in every Texas town that was of any size 150 years ago.
church at Incarnate Word is a hidden jewel IMO bendthelightblog.com/wp-content/uploads/2011…
Modern architecture ...Google O'Neil Ford ..he did Hemispfair Tower, Tower at Trinity etc.
The riverwalk is an archeticture master... Robert Hugman, find his office on the RW, the spiral columns supporting stair cases, Arneson theater, La Vallita etc....again, Google for more info/ sites.
The houses on Kings Highway (street)
Jefferson High School is a master work