Thanks to the wonder of modern technology - here is a top 50. Not sure it picked up everything but there's enough here to keep everyone busy :) I thought everyone on MN hated Paris....
Venice
Grand Canal / canal views
Murano
Burano
St Mark’s / St. Mark’s Square
Vaporetto rides between islands
Lido
Paris
Paris Catacombs
Saint-Denis Cathedral
Pantheon
Pere LaChaise Cemetery
Disneyland Paris
Notre Dame
Rome
Pantheon (Rome)
Vatican
Colosseum
Roman Forum
Trevi Fountain
St Peter’s Basilica (Vatican)
Pompeii
Pompeii amphitheatre
Pompeii ruins
Amsterdam
Anne Frank’s House
Our Lord in the Attic Museum
The Night Watch (Rijksmuseum)
New York City
9/11 Memorial & Museum
Ellis Island
Top of the Rock
Empire State Building
Brooklyn Bridge
Iceland
Blue Lagoon
Northern Lights
Grand Canyon
Helicopter into the Grand Canyon
Colorado River raft
General canyon views
Florence
Florence Cathedral / Duomo
David at the Accademia
Uffizi Gallery
Matera — Old town / Sassi di Matera
Petra
The Treasury (Siq to the Treasury)
Wadi Rum desert
Taj Mahal — 4 mentions :
Mont Saint-Michel
Spain:
Sagrada Família and other Gaudi buildings (Barcelona)
Alh Mezquita (Cordoba)
Alhambra (Granada)
Guernica (Madrid)
Park Güell (Barcelona)
Salt Mines (Krakow)
Cinque Terre
Last Supper (Leonardo da Vinci)(Milan)
Jerash ruins (Jordan)
Pamukkale pools (Turkey)
Great Wall of China
Terracotta Warriors (Xi’an)
Jerusalem Old Town
West Coast of Ireland — Coastal scenery and coastline drives
Culloden battlefield
Wadi Disah Canyon
Neuschwanstein Castle
Wells Cathedral
Bayeux Tapestry
Sana’a Old City
Hagia Sophia
Stonehenge
Acropolis
Cappadocia — (balloon views, cave landscapes)
Iguazu Falls
Bryce Canyon
Grand Teton National Park
Yosemite National Park
The Bund (Shanghai)
Versailles
Westminster Abbey
Forbidden City (Beijing)
Angkor Wat and Ta Prohm (Cambodia)
Uluru (Australia)
Glen Coe (Scotland)
Great Barrier Reef
Krak des Chevaliers (Syria)
Machu Picchu — 2 mentions :
Inca Trail
Machu Picchu
Ha Long Bay - scenery and boats
Ayutthaya — ruins
Marrakesh — Medina and contrasts;