Learn Icelandic: Læknirinn keyrir til Keflavíkur.

The preposition til (meaning "to") always forces the destination into the genitive case. For places ending in -vík (which is a feminine noun meaning bay), the genitive ending is -ur, changing Keflavík to Keflavíkur.

Where is the word for "the" in this sentence?

In Icelandic, the word "the" attaches to the end of the noun. The base word for doctor is læknir. Because it is a masculine noun in the subject position (nominative case), we add the ending -inn to get læknirinn (the doctor).

Why do we use keyrir here instead of keyra?

keyra is the dictionary form (to drive). Because the subject of the sentence is læknirinn (the doctor), we need the third-person singular form (he/she/it drives), which is keyrir.

Can I use til for going to any kind of place?

You generally use til with the genitive case when traveling to a named city, town, or country (like til Keflavíkur or til Íslands). However, for specific buildings or locations inside a town, Icelandic often uses other prepositions.