You’ll find an active, baroque-era basilica in the heart of the colonial center, so expect free entry with a small donation appreciated and a quiet, reverent atmosphere during Mass. Dress modestly and keep your voice down; photography is usually allowed without flash but don’t interrupt services. The plaza and streets around the church are cobblestoned and can be steep, so wear stable shoes and expect limited wheelchair access. Visit early on a weekday to avoid crowds, or pair a late-afternoon stop with a walk around the nearby theater and square, and keep an eye on your belongings in busy areas.