I took a look at all sites without a hotspot assignment. Below a few recommended changes.
The Rome hotspot should include:
* Assisi (2.5h-3h train) and Langobard (Spoleto, 2h train).
The Paris hotspot should include:
* Bourges (2.5h)
* Fontenay (1h Montbard + 5km walk) http://www.abbayedefontenay.com/en/how-to-get-there
The Brno hotspot should include:
The Bavaria hotspot should include:
* Margravial Opera House
The Valencia hotspot should include:
* Teruel (Mudejar)
The Milan hotspot should include:
* Genova (Cinque Terre is included)
The Frankfurt hotspot could include:
* Ice Age Caves (2:40h Blaubeuren by train)
The Hamburg hotspot could include:
* Christiansfeld (4h)
* Corvey (3:30h)
The Toyko hotspot could include:
The Mexico City Hotspot could include:
* Monarch Butterflies
New hotspot: Western Bulgaria (Sofia)
* Pirin is 3h from Sofia. Rila, Boyana and Beech Forest should do the trick.
New hotspot: Stuttgart (overlaps with Frankfurt, but Frankfurt is primarily hotspot due to all the fast trains running).
* Ice Age Caves, Reichenau, Pile Dwellings, Limes, Le Corbusier, potentially Augsburg, Maulbronn, Speyer, Strassburg.
New hotspot: Dijon / Burgendy.
* Dijon, Besancon, Arc-et-Senans, Fontenay
New hotspot: Harz
* Goslar, Hildesheim, Fagus, Corvey.
New hotspot: Missiones (with some good will)
* Paraguay Missions, Argentina Missions, Iguazu 1&2.
New hotspot: Meknes. Fast trains running from Rabat to Fez via Meknes.
* Fez, Volubilis, Rabat, Meknes.
Note: Several sites have 3 components and I think we should maybe more lenient here. Kazan, Istanbul, Vilnius, Kotor/Dubrovnik,