Before 2012 ended I got the chance of going to Luxembourg City.
It is very near to Saarbruecken. You can actually buy a round trip bus ticket for 18 euro.
Given the housing costs in Luxembourg many German and French people work there and live abroad
but there are also many foreigners working there and living in France or Germany.
The nearest German city is Trier, and Metz in france is very very near.
I travelled there using a lorraine, Rhein Pfalz Ticket
so in one single day we(2 friends and I) visited Metz, Luxembourg City
Luxembourg is a nice city, I love its arquitechture and the fact you can
get around either speaking German or French.It is a small city, and to be honest there is nothing much to see, but it is worth seeing, personally I love it.