Where on Earth? Postcards form Europe

Your neighbors, the Wiltons, have gone away on vacation to Europe. Before they left, Mrs. Wilton told all fo the neighbors, "We'll be sending lots of postcards. Try to figure out where each card came form. If you do, we'll throw a block party for everyone when we get back." Then she chuckled and said, "Good luck."
You and your friend Pat looked at each other with satisfied smiles. You figured that this would be a snap. All you'd need to do would be to look at the picture one ach card, and the answer would be obvious. The party would be a sure thing.
Today, the first cards have arrived. AFter supper, your neighbors gather outside and start passing the cards around. You and Pat take a look at them. There are no pictures! One side of each is blank except for an address. The other side has a handwritten message, but no cities or countries are named. From what city and country did the Wiltons write each postcard? Hint: Use an atlas and encyclopedia to find the answers. A dictionary might help too.

The cards read as follows:

Sept. 12: Hi, everybody! Guess where we are? That's right, we want you to guess. Here's a clue: We've spent two days in the largest city of this island country. Must dash--Big Ben says it's time for lunch!
(London, England)

Sept. 14: What country are we in now? A really beautiful one. We sailed through a fjord and hiked on a glacier yesterday. Now we're in the capital, once named after King Christian IV.
(Oslo, Norway?)

Sept. 18: Traveled south and arrived today in the town associated closely with Hans Christian Andersen. Weather here a bit rainy, but we're having too much fun to care!
(??)

Sept. 22: Just flew to this place on the Main River; it's Hesse's largest city. We enjoyed touring the Romer, a town hall built in the 1400s!
(??)

There's a lot more, but I want to get this done first. Please let me know if the first two are correct, and please help me on the last two.
Thanks so much

Yes. Your first two are correct.

To find other answers, Google the key words.

Hans Christian Andersen

Hesse Romer

3. Denmark. But i'm not sure which city

4. Germany? again, i don't know which city

3. (Broken Link Removed)

4. The name of the city practically leaps off the Google search page.

4. Frankfurt

Right.

In front of the Romer in Frankfurt is a big square, surrounded by retail businesses. I visited it just before Christmas a few years ago when it was filled with hundreds of stalls for its Christmas Market. These stalls sold everything from ornaments to clothes to hand-crafted items to food. A big favorite are the stalls selling hot spiced cider or wine.

I still don't know about the third one. i read the article you gave.

You have two choices. One is the town where he was born. The other is the town where he lived later and has a museum for him.