Brussels metro
Brussels has a small Metro network with three lines of metro (two of which share a common section), two lines of "premetro" (underground sections used by otherwise open-air tramway lines and designed so as to be convertible to pure metro lines), and a few short underground tramway sections.
Most of the common section of the two first lines was inaugurated in 1968 as "premetro" (thus with tramways), and was converted in 1976 to the first two lines of actual metro (which was then considered as one line with two branches).
