The walls surrounding the storages, stables and workshops of the Tre Kronor castle are now behind the Lejonbacken and in the basement of the northern row. Thus, Lejonbacken conceals the old windowless wall behind it. Older walls can also be found higher up in large parts of the northern row's facade walls. The walls from the former northeast and northwest square corner-towers for example, are thicker in this part of the palace's ground floor, since Tessin re-used the remaining walls and incorporated them in the new palace. About half of the old walls were used in that manner, since the ever frugal Charles XI had only reluctantly agreed to the conversion which started in 1690. Thrift and recycling were guiding principles at the building of the northern row. Hence, the construction proceeded rather quickly and after five months the new row was topped out and roofed. The new walls became higher than the old ones, except for the towers which were completely enclosed in the new walls. The Charles XI's Gallery is one more feature remaining since before the fire, all according to Tessin's plan.