made to the designs of architect Tony， 是过去分词短语，作one of those additons 的定语。

one of those additons, made to the designs of architect Tony =

one of those additons, which were made to the designs of architect Tony

词组：make additions to ...， 给......添加。

The lead and timber spire was one of those additions, made to the designs of architect Tony.

【翻译】铅材和木质的尖顶是给建筑师托尼的设计额外增加的一部分。