i especially do like the underkroft. >> the underkroft is down a set of stairs underneath the main room of the church. this intricate structure in the basement supports everything above, including the double dome, the arches and an architectural device born of necessity. >> this is the foundation of the building of the american catholic church? >> that's correct. this is the foundation and the building has stood through the weathering of the community, the changes in faith. >> through the 20th century, time was not so kind to the basilica of the assumption as local parish churches grew popular, it lost members. even more, the church lost its luster. >> this church became the church that john carroll didn't want. cathedral. >> in the spring of 2004 it closed its door for a two-year $40 million overhaul. it lost members, but not the city's love. >> for this is my body which will be given up for you. >> its rebirth accomplished with money mostly donated by the citizens of baltimore. it's a church that for nearly 200 years has stood the test of time. its history and symbolism now preserved