Merry wasn’t able to ride a full sized horse by himself, and would have been a burden to both a full grown male warrior and his horse. He would have weighed down the horse, and interferred with the soldier’s ability to fight. Éowyn, being smaller than the average soldier, was able to carry Merry on her horse without slowing it down, as their combined weight was less than that of a fully equipped regular, male warrior. 

Why Didn't Théoden Let Merry Fight In the Battle At Minas Tirith?
This September, I will be flying into Athens at 10:45 PM.  I'll be leaving to Santorini, then arriving back towards the end of the week via Piraeus at 11:45 PM.  

Will arriving that late in town pose any problem traveling to Athenian Callirhoe Exclusiv near the  Parthenon?  Will checkin be a problem?

I see that the hotel is near a metro stop and a bus stop, so hopefully one of those will work.
