One of the most reliable predictors of how rewarding a country is to travel in is whether it has a strong second tier of cities below the capital. Countries with hyper-centralized capitals tend to be one-trip destinations — you visit Paris, you fly home. Countries with strong networks of mid-sized cities reward returning visitors for years.
Italy is the textbook case. Most travelers visit Rome on their first trip, Florence on their second, Venice on their third — and then they discover Bologna, Naples, Turin, Lecce, Palermo, Trieste, Catania, Verona, and they realize the country has thirty cities each with the depth of a capital. Italy is functionally inexhaustible.
Spain is similar (Madrid, Barcelona, Seville, Bilbao, Valencia, Granada, San Sebastián, Salamanca). So is Germany (Berlin, Munich, Hamburg, Cologne, Frankfurt, Leipzig, Dresden). So is Japan (Tokyo, Osaka, Kyoto, Hiroshima, Sapporo, Kanazawa, Fukuoka). So is Mexico (Mexico City, Oaxaca, Mérida, Guadalajara, San Miguel de Allende, Puebla).
Countries that don’t have this depth tend to feel exhausted after one trip. France comes close to monocentric (everything outside Paris feels like Provincial France) — though Lyon, Marseille, Bordeaux and Strasbourg do their best. The UK is similarly London-centric, with Edinburgh, Manchester, Liverpool and Bristol filling out the second tier.
Our recommendation: when planning return visits to a country you love, deliberately bypass the capital. The discoveries are almost always richer.