Basilique St-Sernin.

Standing as one of the largest Romanesque buildings in the West, the Basilique Saint-Sernin is a masterclass in medieval engineering. Built between 1080 and 1117 to honor Toulouse’s first bishop, the structure was designed specifically for the heavy foot traffic of the Santiago de Compostela pilgrimage. Its signature "pilgrimage plan" features an ambulatory and radiating chapels, allowing travelers to circulate past the relics of 128 saints without disrupting ongoing services. Visually, the basilica is defined by its five-tier octagonal bell tower and a striking exterior of alternating brick and stone. Inside, the massive vaulted nave leads to a choir filled with Baroque flourishes and high-relief marble sculptures. Look for the Miègeville door, which remains a benchmark for 12th-century Pyrenean artistry with its intricate depictions of the Ascension.