Not 100% sure about this, but I think the city was one of the first trading ports to be opened up to the colonial powers who wanted in China at the middle of the 19th century...

I imagine once they got in, trade and money changed even the architecture

Tianjin used to be foreign occupied with foreign trade concessions and a lot of the foreign architecture is still around today… though it is disappearing quickly…

A lot of the old house are supposed to be protected but they don't really look like it. Check out the link about the concessions to other countries.

It was once widley used by Germans for trade and even belonged to them the way HK belonged to Britain. Qingdao as well. Then WW1 came along and they lost all their overseas turf.

Well a long time ago at the beginning of 19th century, China was invaded by foreigners such as French, english, German, Japanese, russian, etc...
And they have built theire own monuments as if they were at home, so you can see all kind of churches, ( a french church is nearby the railway station), a russian one by binjiang road and so on...
you will see the streets of Paris right at the central bank of China.
The first time I got there I thought I was back home... haha