At Fretin, a triangular junction links the LGV to the Lille-Brussels HSL 1 high-speed line eastwards, crossing the border at Wannehain and joining the conventional network at Lembeek, south of Brussels. After the Fretin junction, the LGV has a connection to the conventional network at Lezennes, near Lille. This junction is used for TGVs terminating at Lille, which use Lille-Flandres. TGVs that continue beyond Lille, as well as some Eurostar services, stop at Lille-Europe instead. Non-stop Eurostars pass through a tunnel under the city of Lille at .