I haven't built any architectural models for a while, so here goes.
The Cologne Cathedral, designed by Thomas Pleiner for Schreiber Bogen has been around for a while, and for good reason. Beautiful kit, very nicely drawn and coloured, and interesting use of double-sided printing.
JFS 655 Kolner Dom – Kartonmodellbau Online
Lots of open space in the interior structure, but it doesn't affect stability.