Was Jesus crucified at 777 meters above sea level?

Could be. Speaking of Jerusalem, the Catholic Encyclopedia says "the highest point of which, at the northwest corner of the city, is 2577 feet above the level of the Mediterranean". The northwest corner is the traditional site of the Crucifixion.

http://www.newadvent.org/cathen/08344a.htm#II

Now there are 12 inches in 1 foot and each inch is 2.54cm. So the altitude is 2577 x 12 x 2.54 = 78,547cm. Dividing this by 100 gives the altitude in metres, viz 785 metres.

Since no one knows the exact site it's possible it was the 777 metres mentioned. It's also possible it wasn't.

More importantly, perhaps, is the evidence found in Eusebius’ Onomasticon,11 written late in the 3rd century or early in the fourth, some time before Constantine built his basilica on the site of the (destroyed) Temple of Venus. In his notes of various Biblical places he could still find in Palestine, Eusebius wrote of Golgotha: “Place of a Skull,” where the Christ was crucified, which is indeed pointed out in Aelia right beside (pros) the northern parts (tois boreiois) of Mount Zion.

This tends to suggest that the site of the crucifixion — which is what is specifically mentioned by Eusebius — was near the northern parts of “Mount Zion.” Today, Mount Zion is identified outside the southern wall of the city. However, strictly speaking, geographically Mount Zion is the whole of the south-western hill, the “summit” being just south of the present Citadel, where the ground height is 773 m (2536 ft) above sea level. The summit of current Mount Zion is 765 m (2510 ft) above sea level.

Of course there's no way to prove it. Now, modern Jerusalem extends to areas (such as the southern neighborhood of Giloh) which are over 900 meters above sea level, and even the lower altitudes in the city (such as the old tribal boundry of Emek Refaim) are at about 580m above sea level. Seismic activity, biological activity, and the way people measure these things have all changed dramatically in the c. 2,000 years since the event being discussed, so it's highly unlikely that Pilate stopped Jesus at any particular spot for reasons of its altitude relative to the rest of the world at large. The height at which Jesus was nailed up also was probably not above 10 meters (it would have been physically impossible for him to carry a 50-foot beam of wood through those small roads even if he'd had his strength).

Another point is that metres were introduced by the rather un-Christian French revolutionaries in the late 1700s, so Pilate couldn't have known about them. Accurate measurement of heights above sea level wasn't really important then, either. Apart from this, if a particular height was required and for some reason wasn't to be in cubits or such, surely feet or yards would have been used so that modern Americans would understand the height? :)

But It is possible ,however. First of all the roman cubit was the most popular way of measure at that time and it was comparatively consistent and well documented. Bible , as it is written mentions that particular way of system. 1 cubit=44.4cm. Then we often underestimate the technological level of the era. For example Eratosthenis even 300 years B.C managed to calculate the circumference of the earth by using a measuring system using stades, by with remarkable accuracy. And that was almost 300 years before Jesus. The old city of the Jerusalem has a height of 760 meters while the mountain of olives has its highest peak at 850 meters. Even with the geological alterations(dust mostly) anything between 450 to 850 should be taken into consideration. As more unlikely as it is, we cannot exclude any possibility.

I don't understand the point of this question. Why 777? Why meters? Would an equally valid question have been "Was Jesus' burial place at 600 cubits", or whatever.

777 is a number with both Christian and other associations. https://en.wikipedia.org/wiki/777_%28number%29 Apart from which, it is three sevens and three = trinity in more than one religion - see https://en.wikipedia.org/wiki/7_%28number%29#Christianity and scroll down for the others at 7. Additional to my post above, not only were there no metres then but 777 would have been DCCLXXVII (I wonder why Boeing don't use Roman numbers?). Someone has discovered that there is a height above sea level that could be that figure in metres and based a theory on it. A bit like pyramidology in a way. If you look hard enough you can find numbers that fit almost any theory (if you select your units carefully and then multiply some of them by three and divide others by five because it works best five days after the solstice three miles south of Stonehenge making sure you are in a straight line.....).