When Christianity was outlawed in Japan in the early 17th Century many people took their faith underground and are now known by the name kakure kirishitan, "hidden christians". They employed many subterfuges to disguise their faith, perhaps the most well-knoiwn being to equate the Virgin Mary with the Goddess Kannon.
Another was these stone lantern pedestals which originally had a lantern on top to form a cross with truncated horizontals. Hidden Christians are associated most strongly with parts of Kyushu, especially the area around Nagasaki, but these three examples are not from there.
The top photo is from a temple in Ehime, Shikoku, the second from Hagi in Yamaguchi, and the bottom one is in a temple in Tottori.