When I've gone on day trips from Paris, the magic came in two waves. I get a first wave when I go under the arch that says Welcome to
Disneyland Paris on my way from the train station.
On the day trips, my second wave depends on whether I'm going to Disneyland Park or the Studios. When I'm going to Disneyland Park, the magic starts when I hit Main Street. Between the music, the castle, and the familiar surroundings, it's just there! I'm a big veteran of WDW in Florida (hey, it's only 2.5 hours away by plane!), and before I ever went to DLP I wasn't sure how it would be. But as soon as I hit Main Street at DLP, this was DISNEY!!! On my first visit, it felt magical because it felt like I was in WDW. On subsequent trips, it felt magical because I knew I was at DLP! But Main Street at WDW and DLP are fairly similar until you get to the castle (the music is about 90% the same, the buildings are very similar).
I get an equally large wave of magic on my way to the Studios when I see the entrance to the Studios, hear the Hollywood-esque music, and see the Earful Tower. I get another little second wave of magic after leaving Studio One and seeing the "Partners" statue of Mickey & Walt.
On my trip where we stayed on site for multiple days, it didn't feel like I was in Disney until I got to the park and saw that it was snowing. The hotel was gorgeous, and it was magical in its own right, but it didn't hit me that I was in Disney.
Seeing the Princess Parade and hearing that music (Dancin' a Catchy Rhythm) never fails to get me going!!!