Luxembourg Airport (LUX) is 5 miles (8 km) outside the city center.  Two different bus lines go to the center and pass by the Central Train Station as well. They are free of charge as of March 2020. The only other option is a taxi in. 

If you’re coming from the surrounding area, though, the best way to get in is by train. It is comfortable and easy and leaves you walking distance to the city center. Check prices and timetables HERE. 

Once here it’s easy to get around on foot.