In the southern corner of the square, to the right of the town hall and adjacent to it, stands the two-storied Heiligbloedbasiliek (Basilica of the Holy Blood). Kept inside the church is a crystal vial reputed to contain a drop of Christ's blood brought back from the Holy Land by Dietrich of Alsace in 1149 on his return from the Second Crusade. From this has originated the traditional Procession of the Holy Blood when each year in May the sacred relic is carried through the streets of Bruges.

The facade of the basilica with its three Flamboyant-style arches and gilded statues was erected between 1529 and 1534. The basilica itself consists of a Romanesque lower chapel and late Gothic upper chapel. The lower chapel (1149) houses relics of St Basil brought from Palestine by Robert II, Count of Flanders. An elegant spiral staircase leads to the upper chapel (1480) where every Friday the vial containing the Holy Blood is brought out and shown to the faithful.