Many major attractions allow you to reserve your spot and skip the line. Always look online to see if this is an option. This will you to avoid wasting time in multi-hour lines and go right in. It´s normal to see people waiting for hours to enter in the Paris Catacombs, Louvre, London Churchill War Rooms, churches, temples, historic fortresses, and more. Pre-book the day before, skip the line, get to see more during your day!