Answering the Question: Where exactly was Christ when He ascended into heaven on Ascension Thursday?
Here is a quote from The Golden Legend, an early compilation of known Christian history (a.k.a."legends"), written in 1275, by Jacobus de Voragine, Archbishop of Genoa:
As to the first he ascended from the mount of Olives by Bethany; the which mountain, by another relation, is said the mountain of three lights. For by night on the side of the west it is lighted of the fire that burneth in the Temple, which never is put out ne quenched. On the morning it is light of the orient, for she hath first the rays of the sun before it shineth in the city, and also it hath great abundance of oil that nourisheth the light, and therefore it is said the hill of three lights.
Unto this hill Jesus Christ commanded his disciples that they should go. For on the day of his Ascension he appeared two times, one time to eleven disciples that ate in the hall where they had supped with him. All the apostles and the disciples and also the women, abode in that part of Jerusalem which is called Mello, in the mountain of Sion, where David had made his palace. And there was the great hall arrayed and ordained for to sup, whereas Jesu Christ commanded that they should make ready for to eat the Paschal Lamb, and in this place the eleven apostles abode, and the other disciples, and the women abode in divers mansions there about.
And when they had eaten in this hall, our Lord appeared to them and reproved them of their incredulity. And when he had eaten with them, and had commanded them that they should go to the Mount of Olivet on the side by Bethany, he appeared again to them, and answered to them of the demands that they made to him indiscreetly, and with his hands lifted he blessed them; and anon before them he ascended unto heaven.
Of the place of this ascension saith Sulpicius, Bishop of Jerusalem, and it is in the Gloss. For there was edified a church in the place where were made the signs of his ascension. Never sith [afterwards] might be set there any pavement, it could not be laid ne set but anon it issued out, and the stones of the marble sprang into the visages of them that set it. And that is a sign that they be stones on which Christ passed upon, which lie in the powder and dust, and abide for a token and sign certain.
The footprints said to be His are now enclosed in a shrine called the Chapel of the Ascension near the top of the mountain (picture above). The original building was destroyed by the Persians in A.D. 614, but was rebuilt by Crusaders. The Moslems took control of the building in the 13th century and transformed it into a mosque, walling in the arches, and adding a dome, but Christians Jews, and Moslems, alike, claim the building as a religious site -- and as of this writing, all faiths are welcome to visit there.
Unfortunately, though, any visit to this part of the word is a risky venture --- in our day as it has been through the centuries, but the long-standing conflict between Christians and Muslims gotten worse in the last decade than it's been since the crusades I think. When traveling to the Middle East, tourists (brave folks!) are warned against wearing medals or scapulars or other symbols of their Christianity where they can be seen outside clothing. I worry for our son, Paul, who is still on a mission in Jordan -- a country where there are only three Christians to every 100 Moslems. Painful to think that this was the land that Jesus' knew, where His precious feet walked, where His Gospel was first taught. It's a shame to think that we'd take our lives in our hands to travel to the Chapel of the Ascension in order to see for ourselves Christ's footprints in the stone where He ascended into heaven. But, oh my! Wouldn't it be awesome to take the chance! Can you imagine seeing them with your own eyes?