About a month ago I visited the city of Trier which has a rich Roman history.
The best-known Roman building there is the Porta Nigra, built in the last third of the 2nd century AD.
This gate was part of a ca. 6.5 km long city wall.
Porta Nigra is not its original Roman name, btw. The Romans had used sandstone to build this gate, and as you probably know sandstone attracts soot from the air. The name was formed in the Middle Ages when everyone was using coal to heat their houses.
Roman Trier also had three (!) public baths.
One was uncovered right underneath one of their current market squares, and the city council decided to leave it open for the public but to protect it with a big glass house.
Here you can walk among the ruins (notice the carefully placed tarpaulin at the bottom of this photo, generously left behind by the Romans 
), and in one corner watch a very interesting video about another bath, the "Barbara-Therme"
The Barbara-Therme is still being excavated, therefore I couldn't visit it but at least get the above photo 
The name also dates back to medieval times, it is named after the St. Barbara suburb. The Barbara-Therme was built in the middle of the 2nd century AD. Nowadays you can only see about 1/4 of its original size, so huge was it. Not only did they have a cold bath (frigidarium), a luke-warm bath (tepidarium) and a hot bath (caldarium), they also had heated swimming pools!! The Romans sure knew how to live, eh? 
The third public bath is the Imperial bath ("Kaiser-Therme"). Construction started in 293 AD.
It is one of the largest baths from antiquity and four existing building had to be torn down to make way for it and an adjoining sports ground.
Just outside Trier, the Romans started to mine copper ore but the mine wasn't profitable enough so they turned it into a stone quarry. The shafts nowadays are filled with water
On the second photo you can just make out the Roman numbers IV and V, and the letters "Marci" which experts believe is the name of the quarry owner who delivered the stones for the Porta Nigra at the end of the 2nd century AD.
Also nearby Trier but in a different direction, an original Roman villa was partially re-built.
It's in the middle of a housing area, and you can just walk along the former rooms on your own.
The villa had all the luxury you would expect, from floor heating (see last photo) to tepidarium and caldarium all the way to the loo (of course). The toilet building is visible on the left of the next photo. The building on the right is the modern version of it 
It's very interesting, even if you lack the detailed knowledge of an archeology buff (as I do 
)
There are a few more photos on my Webshots homepage, if you're interested.
