Learn Swedish: Är huvudstaden lika vacker som kusten? - Is the capital as beautiful as the coast?

To say "as [adjective] as", Swedish uses lika [adjective] som. In this sentence, lika vacker som means "as beautiful as". The word lika basically means "equally", and som means "as" in this context.

Could I use än instead of som in this sentence?

No. The word än translates to "than" and is only used with comparative words (for example, if you were saying the capital is "more beautiful than" the coast). Because we are saying the two places are equally beautiful using lika, we must use som.

Why is the adjective vacker used instead of vackert?

The adjective describes huvudstaden (the capital). Since stad is an en-word, the adjective takes its basic en-word form, which is vacker. If you were comparing an ett-word, like huset (the house), it would be lika vackert som.

What makes up the word huvudstaden?

It is a compound word made of huvud (head or main) and staden (the city). So, the "main city" is the capital! Notice that the definite ending (the "-en" meaning "the") only attaches to the very end of the compound word, not to both parts.