Came across this interesting interactive map that shows the travelling distances of all 32 teams at the World Cup, individual maps separated by groups are in the second post. https://www.chapman-freeborn.com/en/2018-russia-world-cup-travel-distances/
From FIFA During the group stage of the competition, all teams will stay and train between matches in their TBC (Team Base Camp) and travel from there to the Host City of their respective match, where they will stay overnight at a Venue Specific Team Hotel (VSTH) and have the opportunity to train in a Venue-Specific Training Site (VSTS). In principle, all teams should stay in the VSTH the nights before and after the match in question.
If that's a rule that can't be bent, some teams are screwed, Egypt have the longest distances to cover with over 7000 miles, with Denmark's first game for example they'be be making a 1400 mile round trip from base camp to Saransk, where as it's just a 215 mile trip from Saransk to Samara (2nd game). If it's not a requirement then surely they would have been able to find local facilities good enough to train. In general it's worth looking at the travel distance from base cap for both teams in any match, Nigeria for eg are based in Essentuki near the black sea in the deep south, their first game is in Kaliningrad v Croatia which is a 1238 mile trip, Croatia are based in St Petersburg and will be flying less than half the distance at 513 miles. Nigeria's 3rd game is v Argentina in St Petersburg, a 1217 miles trip, Argentina's base is in Moscow, a 394 mile trip, and that's without factoring the round trips back to base by the time the 3rd match is played.
Will be a lot of tired jet lagged teams at this tournament worth laying on that basis.