milestone, landmark [noun] [de mijlpaal, de mijlpalen]

"Mijlpaal" is composed of
"mijl" and "paal", which respectively translate to "mile" and "pole". The English "milestone"
apparently transforms into a "milepole" in Dutch 🙂 Just like in English the word "mijlpaal" is used to refer to an important event in history or in one’s life, and it is of course also a very popular project management term, see the Examples.

Examples:
– "Vandaag de 500e DWOTD! Een ongelofelijke
mijlpaal, al zeggen we het zelf 😉 ."
("Today it’s DWOTD 500! An incredible milestone, even though we say so ourselves 😉 .")

– "Dit project heeft de volgende
mijlpalen en resultaten:" 
("This project has the following milestones and results:")

– "En, heb je je mijlpaal bereikt, of heeft het werk vertraging opgelopen?" 
("And, have you reached your milestone, or has the work been delayed?" Note the expression "vertraging oplopen": "to get behind", where "vertraging" means delay.)

Related words:
– Prestatie: achievement [noun] [de prestatie, de prestaties].
– Paal: post, stake, pole [noun] [de paal, de palen].
– Kilometer: kilometre [noun] [de kilometer, de kilometers].
– Hectometerpaal(tje): ‘hectometre marker/stone’ [noun] [de paal, de palen].
– Project: project [noun] [het project, de projecten].

Extra:

In the old days, "mijlpalen" or
milestones were used to indicate the distance of one mile relative to a city
gate or next milestone, to inform travellers about their position. The modern
Dutch equivalent is the so-called "hectometerpaal", which is
located along the main roads in the Netherlands ("provinciale wegen" and "rijkswegen"). You often hear the word "hectometerpaal" or its diminutive "hectometerpaaltje" on the Dutch traffic news
to warn you for speed radars along the motorway. When you are not sure about the
speed limit, just check out the speed limit sign on the "hectometerpaaltjes". If there is no speed limit sign, the motorway speed limit
is 120km/h (on a "snelweg").
For more info, see "hectometerpaal"
at Wikipedia.