This 1856 building served as the Norwegian Seamen's Church from 1928 to 1984, according to one recent listing. The co-op conversion occurred in 1986, and the apartments were left with that church conversion trademark, arched windows. There's nothing for sale right now, but prices have averaged $779,000.

This building was constructed as the South Congregational Church in the 1850s. Now it's a condominium with stained glass windows and cathedral ceilings.

The former St. Peter's Church, an 1850s building, went condo in 2004. There's one rather underwhelming 2BR, 2BA available now for $820,000.

There's one co-op on the market now in this converted Brooklyn Heights church. The apartment in question is a 2BR, 2.5BA asking $880,000. Which seems awfully low, but the maintenance is $1,360/month.

This neo-gothic cathedral became a condo building on Fort Greene's Cumberland Street. A 1BR, 1.5BA is up for grabs at the moment, asking $959,000, one of the higher recent prices for the building.

A developer picked up this Bed-Stuy church for $4.1 million in 2008, and crews recently began demolishing the back of the church. Permits call for partial and interior demolition, with Karl Fischer as the architect of record, and the result will be 40 apartments, 31 underground parking spaces, and a community space.

Rentals have just launched at the former St. Vincent de Paul Church rectory in Williamsburg, now a 10-unit residential building. There are a few church remnants—the priciest apartment, on the former parlor floor of the rectory, has floors made from milled beams taken from the actual church next door. (The conversion of the church itself is still in progress.) There are 13 active rental listings, asking between $4,500/month and $5,250/month.

This church isn't open for inhabitants...yet. The building has been seeking a buyer for the past few years, though, and the ads have made much of the possibilities for condo or rental conversion. The property is currently off the market, but perhaps inquiries would be welcomed.

There isn't much of the former Roumanian Synagogue evident in the listing shots for 70 Hester Street. The three-story 1900 building now has two apartments, and its past lives include a stint as a speakeasy. The building is asking nearly $5 million and encouraging renovation for "residential, business or commercial use." Go to it, folks!

The Abbey Condominium is the former parish house of St. George's church, with high ceilings and stained glass still in the units. There are five apartments for sale and seven for rent at the moment. Lowest sale price: $2.19 million. Lowest rent: $7,500/month.

This 1860 Romanesque Revival church is now a condo designed by FLANK—and it's the place where Jude Law threw fruit at NYU students. There's nothing on the market in the building right now, but the average sale price in the past has been $3.612 million.

This Greek Revival church was built in 1846 and converted into a co-op by Stephen B. Jacobs. These days the average sale price is around $1.646 million. Unit #302 is is asking $1.695 million.

The General Theological Seminary's West Building—Chelsea's second-oldest—is undergoing conversion into 23 pricey condos. Preservation specialists Beyer Blinder Belle are helping developer the Brodsky Organization stay within landmark guidelines on this one.

This building used to be a convent, a commenter points out. In fact, it appears to have been the Dominic Convent of Our Lady of the Rosary. Now it's a rental, with units in the $1,500/month to $3,900/month range.

The chapel of this former cancer hospital became a bonkers apartment that took quite some time to sell in its most recent attempt. It finally went for $8 million; the seller had spent somewhere around $5 million on a renovation that added gold leaf and antique French stone floors.