Learn Hardcore German: Selten war das Büro so ruhig wie heute. - Seldom has the office been as quiet as today.

German main clauses follow the verb-second (V2) rule: the finite verb must be the second element. If you put anything other than the subject in first position (here the adverb Selten), the subject moves after the verb. So the order is:

First position: Selten
Second position (finite verb): war
Then the subject: das Büro This is normal German word order after fronting an adverbial. It even mirrors English stylistically: “Rarely was the office so quiet today.”

Can I also say Das Büro war selten so ruhig wie heute? Does it mean the same?

Yes, it’s correct and means the same. Differences:

Selten war das Büro so ruhig wie heute. Fronting Selten adds emphasis on how rare this is and sounds a bit more formal or rhetorical.
Das Büro war selten so ruhig wie heute. Neutral, everyday order.
A third, also common variant is: So ruhig wie heute war das Büro selten. This fronts the comparison for emphasis on “as quiet as today.”

Why is it so … wie and not als?

Use:

so + adjective + wie for equality: so ruhig wie heute (as quiet as today).
Comparative + als for inequality: ruhiger als gestern (quieter than yesterday). Avoid mixing them: not so ruhig als, not ruhiger wie in Standard German.

Why is heute used without a preposition?

Heute is an adverb meaning “today,” so it needs no preposition. Alternatives:

More formal: am heutigen Tag (on this day).
Be careful: heutzutage means “nowadays/in modern times,” not “today.”

Why doesn’t ruhig have an ending here?

After linking verbs like sein/werden/bleiben, adjectives are predicative and take no endings: Das Büro ist/war ruhig. With a noun (attributive), the adjective takes an ending: ein ruhiges Büro, das ruhige Büro.

Could I use present or present perfect instead of war?

Present: Selten ist das Büro so ruhig wie heute. Good if you’re describing the current situation today.
Present perfect (common in speech in many regions): Selten ist das Büro so ruhig gewesen wie heute.
Simple past war is standard in writing and works if you’re looking back on (part of) today or speaking generally in a narrative style. All three are acceptable; choose by context and style.

Is starting with Selten formal or literary?

It’s a bit more rhetorical or emphatic, but still perfectly natural. Everyday alternatives are:

Das Büro war selten so ruhig wie heute.
So ruhig wie heute war das Büro selten. Fronting negative/limiting adverbs like selten, nie, kaum is common for emphasis (compare English: “Rarely was …”).

Where else can I put selten, and does it change the meaning?

All are grammatical; differences are about emphasis:

Fronted (emphasis on rarity): Selten war das Büro so ruhig wie heute.
Midfield/neutral: Das Büro war selten so ruhig wie heute.
End-focus on selten: Das Büro war so ruhig wie heute selten. (more stylistic; sounds advanced)

What exactly does selten modify here?

Selten is a sentence adverb of frequency. It modifies the whole proposition (“the office being this quiet today”), not the adjective ruhig itself. So it means “It is a rare occurrence that the office is as quiet as today.”

What’s the difference between ruhig, still, and leise?

ruhig: calm/quiet, can refer to atmosphere (low activity, little stress) or sound. Broadest word.
still: very quiet/silent; often emphasizes absence of sound.
leise: low volume (quietly/softly), mainly about sound level. Examples:
Heute ist die Stimmung im Büro ruhig. (calm atmosphere)
Die Straßen sind still. (very quiet/silent)
Bitte sprich leise. (speak quietly)

How do I pronounce the tricky words?

selten: [ˈzɛltn̩]
Büro: [byˈʁoː] (rounded ü; stress on second syllable)
ruhig: [ˈʁuːɪç] or [ˈʁuːç] (both common; the final “g” is the “ich”-sound)
heute: [ˈhɔʏ̯tə]

Why is it das Büro? Which case is used?

Büro is neuter; hence the article das. It’s the subject, so it’s in the nominative case: das Büro. The predicate adjective ruhig stays uninflected after sein.

Can I drop so and say ruhig wie heute?

In Standard German, the equality pattern is so … wie. Omitting so (e.g., ruhig wie heute) occurs colloquially, but in careful speech and writing keep so: so ruhig wie heute.

How would I say “as quiet as never before”?

Use so … wie noch nie:

So ruhig wie noch nie war das Büro heute. Avoid combining selten with noch nie in the same comparison; they clash logically.

How would this look in a subordinate clause?

The finite verb goes to the end:

…, weil das Büro so ruhig wie heute war.
…, weil das Büro selten so ruhig war wie heute. Fronting inside a subclause (e.g., weil selten das Büro …) is possible but marked; the neutral order is more natural.