Basílica de San Francisco el Grande

This 18th century basilica houses Spain's largest dome at 33 meters across, actually bigger than St. Paul's in London. You'll walk through seven lavishly decorated chapels arranged in a perfect circle, each telling different religious stories through massive oil paintings. The real draw is Goya's early work in the San Bernardino chapel, where he painted himself as a young man into a scene of St. Bernardino preaching. Zurbarán's intense religious scenes and works by other Spanish masters fill the remaining chapels.

The circular layout creates an unusual flow where you move clockwise through increasingly ornate spaces. The dome dominates everything, its coffered ceiling drawing your eyes upward constantly. Most visitors spend their time craning their necks, but the chapel paintings deserve equal attention. The acoustics are remarkable: whispers carry across the central space while footsteps echo off marble floors. Guided tours take you up into the dome structure and through museum rooms that independent visitors can't access.

Most travel guides oversell this as a rival to major European basilicas, but that misses the point. It's genuinely underrated precisely because it's not trying to compete with the Prado or Royal Palace. Entry costs 5 EUR, guided tours are 10 EUR and worth it for dome access alone. Skip the audio guide and focus on the Goya chapel and dome details. The gift shop is overpriced tourist trinkets, but the small museum upstairs has fascinating architectural drawings.