Beitou has nothing on Nanliao... Pokemon Go wise. Beitou is covered a lot because it's in Taipei, the MRT goes right up to it, and you get swarms of Skydragonites hanging in a small crowded park, blocking tiny streets that the locals use.
Nanliao on the other hand is a nest for EVERYTHING. I mean EVERYTHING. You get a least one Lapras a day. Several pikachus a day. Dratinis are everywhere, so who cares about Dragonites, if you have all day, you can literally get a Dragonite on you own.
Since it's by the ocean, water type pokemons are understandably everywhere. You get Seel and Dewgong, which I have never seen elsewhere, Shellder and Cloyster I also have never seen anywhere else.
Electric type pokemons are aplenty for reasons beyond my comprehension. Pikachus every 30 minutes, Voltorb, Electrode, Magnemite and Magneton all over the place.
Oh, and it has a bunch of ponyta, rapidash, magmar, growlithe and arcanine roaming around.
The best part is the place is huge. Between the harbor area, and the old harbor area which is just a lake at this point, it's a lot of space to run around with no local residents to get mad at you.
The downside is if you go on the weekends, the crowd looks like fifth season finale of the walking dead, when Aaron and Daryl were trapped in the semi-truck lot.