The historic center of the Altstadt of Graz is the trapezoid Hauptplatz – the main square. Already set in 1160 it was then edged by former main roads, known today as the Murgasse, Sporgasse and Sackstraße. The sides of the Hauptplatz are lined by the contiguous facades of four and five storey houses, dating from different eras. In the south sits, the mighty, late historicist Rathaus, the north end of the square heads into the Sackstraße. Focal point of the Hauptplatz is the Erzherzog-Johann fountain built in 1878.

The buildings on the side of square differ in structure: the east side of deeply stretched, medieval townsteads with baroque facades. Worthy of note are the Luegghäuser (Hauptplatz 11 – 12) with stucco facades and hip roofs, the house at Hauptplatz 15 with late Gothic arcades and the house at Hauptplatz 16 with Renaissance arcades and sgraffito decorations. The west side is more of a grown, mixed façade with narrow gabled houses and Baroque town houses, such as the Weiß’sche house (Hauptplatz 3) whose facade has the only colossal pilasters in Graz. Narrow alleys connect the Hauptplatz with the Franziskanerplatz.