The Trocadéro core reused
The record says the Trocadéro's core was reused inside the Palais de Chaillot. The 1889 tower photo shows it standing.
The questionWhat is inside the Palais de Chaillot today?
Investigate · Paris 1878
Exposition universelle - Paris, 1878 by Isidore Laurent Deroy - Gallica
1 clue in this photo
Photo: Isidore Laurent Deroy · Public domain · via Wikimedia Commons
Same kind of clue, elsewhere
Medallions and arcades repeated down the naveWere these ornaments cast for 1876, or are they a standard pattern found in other halls of the era?
The Trocadéro already standing through the archHow many of these 'temporary' fair palaces were left standing for the next fair, and what was there before 1878?
Erechtheion-style caryatid porchesWhy does the same classical vocabulary turn up fair after fair, city after city?
Greece and Egypt on one groundWhy do Greek and Egyptian forms keep turning up together at these fairs?
A skyline of ornate towersWere towers like these power infrastructure first and decoration second?
The long-hall formula againWhy does the same long-hall plan recur from city to city, and who held the pattern?