Plane:
There are two airports in Beijing, Beijing Capital International Airport (北京首都国际机场, PEK) and Beijing Daxing International Airport (北京大兴国际机场, PKX). Here lists the driving distance/duration (assuming good traffic) between both airports and the conference hotel.
PEK: 61 km, ~ 60 min
PKX: 119 km, ~ 100 min
Train:
Here lists the driving distance/duration (assuming good traffic) between the conference hotel and different train stations.
FYI, there are trains between Beijing North and Huairou stations, although not very frequent.
Beijing West (北京西站): 74 km, ~ 100 min
Beijing South (北京南站): 77 km, ~ 100 min
Beijing Station (北京站): 68 km, ~ 80 min
Beijing North (北京北站): 67 km, ~ 80 min
Beijing Chaoyang (北京朝阳站): 64 km, ~ 70 min
Beijing Fengtai (北京丰台站): 82 km, ~ 110 min
Huairou Station (怀柔站): 10 km, ~ 19 min
Huairou North (怀柔北站): 6 km, ~ 13 min
Huairou South (怀柔南站): 16 km, ~ 22 min
