For the price of one

Question

_{This puzzle is part 12 of Gladys' journey across the globe. Each part can be solved independently. Nevertheless, if you are new to the series, feel free to start at the beginning: Introducing Gladys.}

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Dear Puzzling,

A new day, a new city. Once again, there is so much to see that I don't even know where to start. Good thing that I'm not in a hurry! I'm writing to you from a small island in full view of not one but two of the world's most iconic landmarks (granted, one of them is a replica).

Wish you were here!
Love, Gladys.

Crossword across
1. Prophetic sign
6. Mental disorder
9. Learned, knowing
10. Metal vocalist with an eponymous band
11. Thor's enemy in comic books
12. The most resilient parasites
13. 100 centavos
15. Illuminance unit
16. Of course, in a text message
18. Football organization
21. Tubers
22. Firearm
23. Native American tribe
24. Body of water

Crossword down
1. To have debt
2. Denver's elevation
3. Prominent landform
4. Taker of a small step
5. Actor Alan
7. French for "God"
8. Elaborate fabrication
13. Rolls –
14. Company name in Looney Tunes
15. Edible parts of frogs
17. Payment for transport
18. Purposes or benefits
19. Combustible material
20. Actress Ortiz

Cryptic across
1. A feline particle (4)
6. Funny tags for a buck (4)
9. Currency in Portugal, Iraq... (4)
10. Total amount in consumption (3)
11. Wild, detailed, extremely elaborate ruse (4)
12. To half-heartedly meet around a pole (5)
13. Punch vegetable audibly (4)
15. Linux icon Torvalds's first user experience (3)
16. Curve a relic's sides (3)
18. Behold West End's leading actor Rob (4)
21. Elusive mountain dweller is still single (4)
22. Spirit endlessly getting older (3)
23. With no end in sight, make fun of lack of difficulty (4)
24. Elderly, polled regularly (3)

Cryptic down
1. Boxer to strike guy in Manila, making comeback (3)
2. Top element missing from upcoming first-class block (4)
3. Film's music lacks opening for central part (4)
4. Glossless finish missing for actor Damon (4)
5. Listen to a spouse briefly leading to gas station (4)
7. Anglican priest's ballet dress (4)
8. Corrupted exam card (4)
13. Mathematician's central thesis follows director Michael (5)
14. Lloyd Webber musical switches first two parts of play (4)
15. African country also surrounds Ghana's capital (4)
17. Enjoy books, fear no introduction (4)
18. Heartless Facebook votes are fabrications (4)
19. First signs of Winston, in leadership, trusting Chamberlain (4)
20. Finish Pernod evenly (3)

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_{Gladys will return in "Better than Rembrandt".}

Answer 1

You are

on the Ile aux Cygnes, in the River Seine, in Paris.

Clues and solutions:

Crossword across                                 |       Cryptic across
 1a. Prophetic sign                        OMEN  | ATOM   1a. A feline particle (4)
 6a. Mental disorder                       ADHD  | STAG   6a. Funny tags for a buck (4)
 9a. Learned, knowing                      WISE  | LIRA   9a. Currency in Portugal, Iraq... (4)
10a. Metal vocalist with an eponymous band DIO   | SUM   10a. Total amount in consumption (3)
11a. Thor's enemy in comic books           HELA  | WILE  11a. Wild, detailed, extremely elaborate ruse (4)
12a. The most resilient parasites          IDEAS | TOTEM 12a. To half-heartedly meet around a pole (5)
13a. 100 centavos                          REAL  | BEAT  13a. Punch vegetable audibly (4)
15a. Illuminance unit                      LUX   | TUX   15a. Linux icon Torvalds's first user experience (3)
16a. Of course, in a text message          OFC   | ARC   16a. Curve a relic's sides (3)
18a. Football organization                 UEFA  | LOWE  18a. Behold West End's leading actor Rob (4)
21a. Tubers                                YAMS  | YETI  21a. Elusive mountain dweller is still single (4)
22a. Firearm                               GUN   | GIN   22a. Spirit endlessly getting older (3)
23a. Native American tribe                 CREE  | EASE  23a. With no end in sight, make fun of lack of difficulty (4)
24a. Body of water                         SEA   | OLD   24a. Elderly, polled regularly (3)

Crossword down                                   |       Cryptic down
 1d. To have debt                          OWE   | ALI    1d. Boxer to strike guy in Manila, making comeback (3)
 2d. Denver's elevation                    MILE  | TILE   2d. Top element missing from upcoming first-class block (4)
 3d. Prominent landform                    MESA  | CORE   3d. Film's music lacks opening for central part (4)
 4d. Taker of a small step                 NEIL  | MATT   4d. Glossless finish missing for actor Damon (4)
 5d. Actor Alan                            LADD  | ESSO   5d. Listen to a spouse briefly leading to gas station (4)
 7d. French for "God"                      DIEU  | TUTU   7d. Anglican priest's ballet dress (4)
 8d. Elaborate fabrication                 HOAX  | AMEX   8d. Corrupted exam card (4)
13d. Rolls –                               ROYCE | BAYES 13d. Mathematician's central thesis follows director Michael (5)
14d. Company name in Looney Tunes          ACME  | ACTS  14d. Lloyd Webber musical switches first two parts of play (4)
15d. Edible parts of frogs                 LEGS  | TOGO  15d. African country also surrounds Ghana's capital (4)
17d. Payment for transport                 FARE  | READ  17d. Enjoy books, fear no introduction (4)
18d. Purposes or benefits                  USES  | LIES  18d. Heartless Facebook votes are fabrications (4)
19d. Combustible material                  FUEL  | WILT  19d. First signs of Winston, in leadership, trusting Chamberlain (4)
20d. Actress Ortiz                         ANA   | END   20d. Finish Pernod evenly (3)

Presumably IDEAS is a reference to memes, but I'm not sure why "most resilient". [EDITED to add:] Ah, apparently it's from Inception.

Grid:

        M   L                C   E
    O M E N A D H D      A T O M S T A G
    W I S E D I O        L I R A S U M
  H E L A I D E A S    W I L E T O T E M
    R E A L L U X        B E A T T U X
    O F C U E F A        A R C L O W E
    Y A M S G U N        Y E T I G I N
    C R E E S E A        E A S E O L D
    E E   S   L          S D   S   T

and now

the matching letters (with "?" where I can't tell whether they match) are as follows:

        .   .
    . . . . . . . .
    . I . . . . .
  . . L . . . . . .
    . E A . . U X
    . . C . . . .
    Y . . . G . N
    . . . E . . .
    . .   S   .

spelling out ILE AUX CYGNES -- from which one can see (1) a replica of the Statue of Liberty, and (2) the actual Tour Eiffel.

Credit where due:

El-Guest found HELA as Thor's enemy, which I wouldn't have found not only because I don't know anything about comics but also because I had NESS for 3dn -- which is a perfectly good answer in isolation, but as El-Guest says presumably the intended answer is MESA. JonMark Perry noticed that I hadn't done 14d (I had all the letters and never even looked at the clue!) and also provided the answer. Chris Cudmore revealed that "Ideas are the most resilient parasite" is indeed a quotation, from the movie Inception.