For this achievement, you need to view 100 different landmarks from 550 yards or less for at least 3 seconds. I normally wait until I am 0.3 NM away to start using smart view. Despite the achievement description, they do not need to be star locations on the map.
Also something to note: if you are in an area with multiple landmarks that are very close to each other, when you use smart view on one, it will count all landmarks (within 550yds) after viewing the first one for 3 seconds (or at least it did for me). I would suggest that you open up the gamebar (Windows key + G) and pin the achievement tracker so that you can actively see when progress increases.
You don't have to depart an airport, so you can spawn from any point on the map, and you can slew (Y key I believe) in between landmarks. However I would avoid altering sim rate since you have to view for 3 sec.
Here is a [not all inclusive] list of what airports (by ICAO) that have landmarks near them. (I will be using abbreviated directions, ie: East North East will be ENE, which, if you're unfamiliar with compass directions, means that it is half way between East and North East)
HEBF - Egypt - has 11, Just go north from the airport and you should find them all.
ZBBB - Beijing - 9 are located going North, then circling to the East
LFPZ - Paris - 8 are located ENE
VHHH - Hong Kong - 8 E
OMDB - Dubai - 7
ZSSS - Shanghai - 7 ENE
EGLC - London - 6 W
VMMC - Macao - 6 NW
RJTT - Tokyo - 5 NNE
WSSI - 5 NE
LTBA - 4 ENE
KEWR - NY - 4 E
RCSS - 3
WMKF - 3
OE49 - 2 W
EHAM - 2 N
EPBC - 2 SE
LFOD has 4 going ENE, with LFOQ being a middle point, but you might miss some, just follow the river.
The following have 1:
Z14D 1 NE 1 SW
Some of these may be far away, but this is what I used to get it, so good luck!