Mikveh in a bad neighborhood - Igrot Moshe Yoreh Deah 2:91

In a strange case brought to Rav Moshe Feinstein in 1964, the question was asked about the status of a mikveh in a non-Jewish neighborhood which apparently had windows that allowed passers-by to look into the mikveh. Rav Moshe begins by decrying this as a major breach of tzniut, and then notes that the טבילה that the women do may not be good, as they might be so self-conscious as to not be careful with what they are doing. He further exhorts the community to take whatever measures necessary to construct a mikveh that is not compromised.

Rav Moshe then addresses the issue of how the new mikveh is to be built. Apparently, the community wanted to destroy the existing mikveh in order to build the new one. However, Rav Moshe notes that this would leave the community without a functioning mikveh for the intervening period, and that would be an untenable situation.

An additional issue raised was whether or not the community should be worried that a non-Jew would climb up on the roof of the new mikveh and pour water into the pit that was collecting rain water for the mikveh, thus invalidating the mikveh. Rav Moshe ruled that we do not worry that a non-Jew would do something like this, which involves a certain degree of effort, if he stands to gain nothing.

Finally, the questioner asked as well about a community who wanted to construct a shul so that the Aron and bima could be automatically lowered out of sight in the event that a wedding would take place in the shul. Rav Moshe rules unequivocally that such a move would be forbidden, as it would not be respectful to the Torah for it to be below the floor while people are celebrating above (and not necessarily celebrating in a halachically acceptable fashion). Furthermore, Rav Moshe points out that the Chatam Sofer and others do not approve of using shuls as venues for weddings.