The first European trip is about the postcard — the cathedral, the palace, the medieval square. The second trip is about figuring out where the locals actually live and discovering that you'd rather have stayed there the first time.
This is a per-city tour of the neighborhoods that fit that pattern: the place residents go on Saturday mornings, the place where rent has been climbing for the last decade, the place that quietly has the best food.
Paris — the 11th and 10th
The 4th, 6th, and 1st arrondissements are the postcard answers. The 11th and 10th are where Parisians under 40 go out on Friday. Bastille in the 11th has restaurant density that the 4th can't match at half the prices.
Berlin — Kreuzberg and Neukölln
Mitte is the museum-island answer. Kreuzberg is where the food, the nightlife, and the actual Berliners are. Neukölln (further out, no neighborhood page yet) is where the gentrification frontier is currently pushing.
Lisbon — Príncipe Real and Estrela
Bairro Alto is the loud-bar district; Alfama is the postcard hill. Príncipe Real is where you actually want to live — design shops, leafy plazas, weekend brunches. Estrela (no neighborhood page yet) is the slightly quieter older sibling.
Madrid — Malasaña and La Latina
Sol/Centro is for tourists. Malasaña is for under-40 Madrileños. La Latina is for everyone on Sunday afternoons (Cava Baja, the rastro).
Barcelona — Gràcia and El Born
Las Ramblas is a tourist trap. The Gothic Quarter is overrun. Gràcia is the village-feel residential district; El Born is the cooler younger sibling of the Gothic Quarter.
Rome — Trastevere and Monti
Centro Storico is for first-timers. Trastevere is for second-timers (and most Romans on Saturday nights). Monti is the design-shop, hilly underrated middle option.
Amsterdam — Jordaan and De Pijp
The Centrum is partial-stag-do hell. Jordaan is the canal-belt charm answer; De Pijp is the food-and-evenings answer.
Istanbul — Beyoğlu and Kadıköy
Sultanahmet is the historical-sights answer for first-timers. Beyoğlu (Galata, Karaköy, Cihangir) is where second-time travelers stay. Kadıköy on the Asian side is where Istanbul actually lives.
Prague — Vinohrady and Žižkov
Old Town is loud and overpriced. Vinohrady is leafy, residential, the city's best dinner radius. Žižkov is rougher and the bar-density capital of central Europe.
Vienna — Neubau and Leopoldstadt
District 1 is grand-Vienna. Neubau (District 7) is design-shop-creative-mid-priced. Leopoldstadt across the canal is the underrated calm-and-cheap answer.
Budapest — District VI and Erzsébetváros
District V is the polished-tourist answer. District VI is the Andrássy Avenue mid-tier. District VII is the ruin-bar epicenter (loud).
Stockholm — Södermalm
Gamla Stan is the postcard. Södermalm is where the design-magazine version of Stockholm actually lives.
Copenhagen — Vesterbro and Nørrebro
Indre By is the polished tourist core. Vesterbro is the food-and-design answer. Nørrebro is the calmer, more diverse, cheaper alternative.
The pattern
In every case the local neighborhood is 5-15 minutes by tram or metro from the postcard center. The trade-off is real but small. The reward — better food, lower prices, calmer evenings, actual Europe rather than tourist-Europe — is large.
Pick the postcard for trip one. Pick the locals' neighborhood for trip two. By trip three, you've found your own rhythm.