Roman Catholics make the Sign of the Cross when passing a Catholic church, because each church houses the Blessed Sacrament, the Real Presence of Christ on Earth. Since each Catholic church houses the Blessed Sacrament, each church building can be viewed as a very large tabernacle. I have heard of people who, not to be put off by locked churches, travel about in their car, stopping at various Catholic churches to spend time in prayer outside of each, viewing each building as a tabernacle; hence making a mini-pilgrimage in their own town or city.
It is beautiful (and startling!) that Our Lord remains with us, in this often dark and unsettled world, in the Eucharist. We often look for signs and wonders, perhaps promoted by questionable attention seekers, but for those with eyes to see there is a wonder in each Catholic church: Christ Jesus. There, where Christ resides, we might sing:
Let all mortal flesh keep silence,
And with fear and trembling stand;
Ponder nothing earthly minded,
For with blessing in His hand,
Christ our God to earth descending
Comes our homage to demand.
King of kings, yet born of Mary,
As of old on earth He stood,
Lord of lords, in human vesture,
In the body and the blood;
He will give to all the faithful
His own self for heavenly food.
Rank on rank the host of heaven
Spreads its vanguard on the way,
As the Light of light descendeth
From the realms of endless day,
Comes the powers of hell to vanquish
As the darkness clears away.
At His feet the six winged seraph,
Cherubim with sleepless eye,
Veil their faces to the presence,
As with ceaseless voice they cry:
Alleluia, Lord Most High! source