What did the money for indulgences fund?

In Luther"s time it financed the construction of what we now know as St.Peters church in Rome the showpiece of the Vatican. it may also have financed the Viper-like collonade tunnels which lead up to the Church Building proper and suggest almost a modern (Artificial Tunnel) like those on the Denver & Rio Grande and temporary ones to all pedestrian (and out of the weather) access around construction sites, minimizintg falling-debris accidents. I have seen many of these (Tunnels) in NYC.