Puer sursum in turrim ascendit, ut totam urbem videat.

Because puer is the subject of ascendit. In Latin, the subject of a finite verb is normally in the nominative case.

So here:

• puer = the boy
• ascendit = climbs / climbed

Therefore, puer is nominative singular.

Sursum is an adverb meaning up, upward, or upwards.

A learner might wonder why it is needed, since ascendit already suggests upward movement. The answer is that Latin often uses an adverb like sursum for emphasis or vividness, much as English can say climbed up even though climbed already implies upward motion.

So sursum ascendit is a natural way of saying went up / climbed up.

Because in takes different cases depending on its meaning:

• in
  • accusative = motion into or toward
• in
  • ablative = location in or on

Here the boy is moving, so Latin uses the accusative:

• in turrim = into the tower / up to the tower

If you wanted to say in the tower as a location, you would use the ablative:

• in turri = in the tower

It can be understood a little flexibly in English.

Latin is marking motion toward/into the tower with in + accusative. Because the verb is ascendit and the adverb sursum is also present, the whole phrase suggests upward movement involving the tower.

Depending on context, English might translate it as:

• into the tower
• up the tower
• to the top of the tower

The important grammar point is that the accusative shows movement, not rest.

Here ut means so that or in order that.

It introduces a purpose clause: it explains why the boy climbed up.

So:

• ut totam urbem videat = so that he may see the whole city

Because after ut in a purpose clause, Latin normally uses the subjunctive, not the indicative.

So:

• videt = he sees or he is seeing
• videat = that he may see / so that he might see

This is one of the most important uses of the subjunctive in Latin: purpose.

Videat is:

• 3rd person singular
• present subjunctive
• active
• from video, videre

So it means something like:

• he may see
• he might see
• he can see in a purpose sense

Its subject is still puer, even though puer is not repeated.

Because urbem is the accusative singular form of urbs.

Here it is the direct object of videat:

• videat quid? = see what?
• urbem = the city

So Latin uses the accusative.

Totam is an adjective meaning whole or entire, and it agrees with urbem in:

• gender: feminine
• number: singular
• case: accusative

So:

• urbs = nominative singular
• urbem = accusative singular
• tota would be nominative feminine singular
• totam must be accusative feminine singular to match urbem

That is why Latin says totam urbem = the whole city.

Because Latin word order is much freer than English word order.

Placing the adjective before the noun is very common, so totam urbem is perfectly normal. Latin could also say urbem totam, but that might give a slightly different emphasis.

For a learner, the key point is this: the endings show the grammar, so word order is often chosen for style or emphasis rather than basic sentence structure.

Not in the same rigid way as in English.

Latin relies heavily on inflected endings, so the roles of the words are mostly clear even if the order changes. This sentence has a very natural order:

• Puer = subject first
• sursum in turrim ascendit = the main action
• ut totam urbem videat = purpose clause at the end

That final placement of the purpose clause is especially common and elegant in Latin prose.

It can mean either, depending on context.

The form ascendit can be:

• present: he climbs / is climbing
• perfect: he climbed / has climbed

This is a common point of confusion for learners, because some 3rd person singular present and perfect forms look identical.

So context, or the translation already provided, tells you which sense is intended.

That is a very good question.

In classical Latin, if the main verb is clearly past, you often expect an imperfect subjunctive in a purpose clause:

• ascendit, ut videret

However, ascendit is ambiguous in form and may be understood here as present. Also, beginner sentences often simplify or focus on one construction at a time.

So the practical answer is:

• videat is the normal present subjunctive for a purpose clause
• if the sentence were clearly framed as past in strict classical sequence, videret would often be expected

Yes.

Since ascendit already means he climbs/climbed, Latin does not need to state the subject pronoun or noun unless it wants to make the subject explicit.

So Latin could say:

• Sursum in turrim ascendit, ut totam urbem videat.

But adding puer makes the subject clear and is especially helpful in a teaching sentence.