My friend is preparing for her upcoming round-the-world trip and is excitedly making lists of places she wants to visit. She sent me a list of her current top 20 destinations. Mostly I see what the names refer to, but there's one that seems ambiguous and I can't figure out where in the world it is. Anyway, here is the list.

In Europe she's interested in seeing the historical site of Knossos, the narrow Spreuerhofstraße street as well as the headquarters of the International Criminal Court.

Apparently she really wants to see the Martyrs' Memorial in Algeria. Other African destinations on her list are the Fortress of São Miguel and Liberia's Ducor Palace Hotel.

It looks like she intends to spend quite some time in Asia. The Nehru Science Centre and Fort Cornwallis are on her list. In China she wants to see the Bird's Nest stadium, walk in the Dawei Mountain National Forest Park and check out Zhanqiao Pier. The remaining Asian targets are the E-World 83 Tower and the Nakasu red lights district.

From what I can see she only has one Oceanian destination listed – Surfers Paradise in Australia.

In the Americas she on the other hand has quite a few points of interest. She wants to see Granville Island and Copper Square, visit the Biosphère museum and take a tour in Fort Fincastle. She also really wants to see the Mitad del Mundo monument which marks the equator.

There is one item on her list that I can't place on a map. She has written just Presidential Palace. Lots of countries have presidents and I assume a ton of them have some sort of presidential palace. I wonder which one she is talking about.

Can you help me figure out which presidential palace my friend wants to visit?


The puzzle would not work if the list had 19 or 21 places instead of 20.

Hint #2:

Granville Island could be replaced by Carlton Gardens, but not by the Stampede Grandstand.

  • 5
    $\begingroup$ I'm intrigued.. I almost just want to go on this trip vs solve it! $\endgroup$ Commented Oct 8, 2018 at 14:19
  • 2
    $\begingroup$ Does your friend happen to be Carmen Sandiego? $\endgroup$ Commented Oct 16, 2018 at 14:51

2 Answers 2


It's so exciting when you figure out the answer! I think I got it.

The second hint was crucial, since I realized Vancouver (location of the Granville island) and Melbourne (where the Carlton Gardens are) have one thing in common:

the diphthong. And there happens to be exactly 20 diphthongs without repeating letters in the English language.

Let's take a look at what we got:

Ae: Daegu (E-World 83 Tower)
Ai: Mumbai (Nehru Science Centre)
Ao: Qingdao (Zhanqiao Pier)
Au: Nassau (Fort Fincastle)
Ea: Montreal (Biosphere Museum)
Ei: Beijing (Bird's Nest)
Eo: George Town (Fort Cornwallis)
Eu: Reutlingen (Spreuerhofstraße)
Ia: Monrovia (Ducor Hotel)
Ie: Algiers (Martyrs' Memorial)
Io: Heraklion (Knossos)
Iu: Liuyang (Dawei National Park)
Oa: Gold Coast (Surfers Paradise)
Oe: Phoenix (Copper Square)
Oi: ????
Ou: Vancouver (Carlton Gardens)
Ua: Luanda (Fortress of São Miguel)
Ue: The Hague (ICC HQ)
Ui: Quito (Mitad del Mundo)
Uo: Fukuoka (Nakasu)

A presidential palace in a city with "oi" in it? That would be the presidential palace in Hanoi, Vietnam!

  • 2
    $\begingroup$ That's genius! It's been driving me mad $\endgroup$
    – Mohirl
    Commented Oct 16, 2018 at 13:54
  • 2
    $\begingroup$ This is correct. Well done! $\endgroup$
    – Jafe
    Commented Oct 16, 2018 at 22:26

Let’s look at the

cities/regions where these places are located:


Crete, Greece


Reutlingen, Germany

Headquarters of the International Criminal Court.

The Hague, Netherlands

Martyrs' Memorial in Algeria.

Algiers, Algeria

Fortress of São Miguel

Luanda, Angola

Ducor Palace Hotel.

Kumasi, Ghana

Nehru Science Centre

Worli, Mumbai, India

Fort Cornwallis

Penang, Malaysia

Bird's Nest

Beijing, China

Dawei Mountain National Forest Park

Yunnan, China

Zhanqiao Pier.

Shandong, China

E-World 83 Tower

Daegu, South Korea

Nakasu red lights district

Fukuoka, Japan

Surfers Paradise in Australia.

Gold Coast, Australia

Granville Island

Vancouver, Canada

Copper Square

Phoenix, Arizona

Biosphère museum

Montréal, Canada

Fort Fincastle

Nassau, Bahamas

Mitad del Mundo monument

Quito, Ecuador

Presidential Palace

I noticed that there’s a diversity of letters here — almost every letter is used in the city names or country names, except for one: Z. I’d therefore postulate that the Presidential Palace she’ll visit is the one in Zagreb, Croatia.

  • 2
    $\begingroup$ You may be on to something, but this is not the intended answer. I've made an edit to disambiguate the Ducor Palace Hotel (apparently there are several with the same name). $\endgroup$
    – Jafe
    Commented Oct 8, 2018 at 19:01

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