What's the must-see thing in Buenos Aires?

The building opened in 1908 after two of its three architects died before seeing it completed — which gives you a sense of the project's weight. The foyer smells like old wood polish and something faintly sweet from the marble. Stand in the main hall and clap once: the sound comes back from every direction with a warmth that recording engineers still travel here to capture. Caruso sang on this stage. Stravinsky conducted from this pit. The stained glass ceiling, imported pane by pane from France, throws colored light across the upper balconies around 10am when the morning sun comes through at the right angle. Guided tours run every 15 minutes starting at 9am, cost around 3,000 ARS (roughly $3 USD at current blue-dollar rates), and last about 50 minutes. Go on a weekday morning — weekend tours fill with school groups that make it hard to hear the guide. If you can catch an evening performance, the cheapest seats in the upper paraíso section run 5,000–15,000 ARS, and the acoustics are actually better up there than in the expensive stalls below. That's not marketing speak. The horseshoe shape sends sound upward.

Recoleta Cemetery is the second stop, and it's free. The entrance sits on Junín street next to the Basílica del Pilar — walk past the weekend craft fair if you're visiting Saturday or Sunday. Inside: 4,800 above-ground marble vaults packed into narrow corridors that feel more like a miniature stone city than a graveyard. The marble is cold to the touch even when it's 30 degrees outside. Cats sleep on the tombs. You'll hear tour guides echoing off the walls in four or five languages at once. Everyone finds Evita's vault eventually — it's marked by fresh flowers that someone replaces daily — but the real reason to come is the stonework at arm's reach. Art Nouveau angels next to neo-Gothic spires next to Egyptian revival doorways, packed so tight you could touch three different centuries of funerary architecture without moving your feet. Budget 45 minutes. The cemetery closes at 5:30pm and the guards start pushing people toward the exit at 5:15, so don't show up late.

San Telmo's Sunday market is the third pick, and the day matters — the rest of the week the neighborhood is quiet to the point of feeling deserted. The Feria de San Telmo runs along Defensa street from roughly 10am to 5pm, and the whole area fills in. Tango dancers set up on the cobblestones at Plaza Dorrego, the air carries smoke from choripán grilling on portable parrillas, and antique dealers spread tables with mate gourds, old soda siphons, and leather goods that range from actual vintage to last-Tuesday vintage. The crowd gets dense by noon. If you want to browse without shuffling shoulder-to-shoulder, arrive by 10:30. For lunch, skip the overpriced tourist places lining Defensa and walk one block east to Bolívar — El Federal on the corner of Carlos Calvo has been open since 1864 and serves a milanesa napolitana the size of your forearm for around 8,000 ARS.

A word on what to skip. Every other guide will send you to La Boca for the painted houses on Caminito. Here's the thing: Caminito is three blocks of color-saturated photo backdrop surrounded by a neighborhood where locals will tell you not to walk with your phone visible. The paint gets refreshed on a schedule by the city tourism office. It looks the same in every photo taken over the last 30 years because it is, functionally, a stage set. If you've done Teatro Colón, Recoleta, and San Telmo on Sunday, you've given your time to things that are real rather than performed. That said, if Boca Juniors happens to be playing at La Bombonera while you're in town, that changes the equation — the concrete stands shake when 50,000 people jump in unison, and the noise hits you in the chest. Tickets through the club's website run 15,000–30,000 ARS. But that's a football experience, not a Caminito one.