At a temple in Japan recently I had the experience of "entering the womb of the Buddha." This involved going into pitch-black chambers beneath the temple (there is a handrail for guidance), round a few corners and into a small room with a dimly lit Sanskrit seed syllable carved in stone. Although I didn't know it at the time, you are supposed to turn the stone and make a wish. Since it was a special Autumn opening of the temple at night, there were hundreds of people there and the experience in the "womb" was mostly one of hearing a lot of giggling and making sure I didn't inadvertently grope the woman in front of me.

It turns out that the seed syllable represented Daizuigu Bosatsu, the Buddha's mother, who apparently is a boddhisattva who can grant any wish. But as far as I can make out, "womb of the Buddha" is actually a Mahayana term meaning "Buddha nature" and it refers to the womb of the Buddha-to-be. Perhaps the idea is that we all nurture the potential to be a Buddha in the same way that Maitreya, the official Buddha-to-be, awaits his inevitable buddhahood.

This is a typical example of the kind of cute stuff some Japanese temples provide for domestic tourists, but it's quite a contrast with the more serious activities of pilgrims you see on pilgrimage routes there.

Interesting. As in the Sanskrt garbha, 'womb'. Dhatugarbha (a euphemism for stupas), Tathagatagarbha, Buddhagarbha etc.