Learn Hardcore Japanese: ike no tikaku no hodou wo sanposimasu. - I take a walk on the sidewalk near the pond.

The first の links 池 (pond) with 近く (vicinity), literally “the vicinity of the pond.”
The second の turns that phrase (池の近く) into an adjective for 歩道 (sidewalk).
So it reads as “the sidewalk of the vicinity of the pond,” i.e. “the sidewalk near the pond.”

What part of speech is 近く and what does it mean here?

近く is a noun meaning “vicinity” or “nearby area.”

When used with に (as in ～の近くに～), it tells you where something exists.
When used with の (as here), it modifies another noun: 近くの歩道 = “the sidewalk in the nearby area.”

Why can’t we say 近くに歩道 instead of 近くの歩道?

Particles serve different roles:

に marks a location or target (adverbial use). You’d say 駅の近くに店があります (“There’s a shop near the station”).
の creates an adjective phrase from a noun. To directly modify 歩道, you need の, giving 近くの歩道 (“the sidewalk that is near”).

Why is there an を after 歩道, but no particle between 散歩 and します?

散歩する is a compound (suru-verb). The noun 散歩 attaches directly to する without を.
歩道 is the object of the action “to take a walk.” Objects need を.
So: 歩道を散歩します = “(I) walk on the sidewalk.”

Can we replace 散歩します with 歩きます?

Yes, both mean “to walk,” but nuance differs:

散歩します implies taking a leisurely stroll or “going for a walk.”
歩きます simply describes the physical act of walking (e.g. walking somewhere to get there).

Why is the subject omitted in this sentence?

Japanese often drops the subject when it’s clear from context. Here, it’s understood that the speaker (I/we) is doing the walking. Adding 私は (“I”) is possible but often unnecessary in everyday speech.

How is the word order in Japanese different from English in this sentence?

In Japanese: modifier → noun → object marker → verb.
池の近くの (modifier) → 歩道 (noun) → を (object) → 散歩します (verb).
In English we’d say, “I take a walk on the sidewalk near the pond,” but Japanese places all modifiers before their nouns and the verb at the very end.