A sitewide architecture deliverable can and often does take many forms.
The most common architecture deliverable is probably a sitemap. Sitemaps can range from very high-level to very granular. A static sitemap diagram is often sufficiently useful and informative for smaller sites. For larger sites, an interactive sitemap can be more useful. Lately, we’ve been using SlickPlan for our interactive site mapping needs. Sitemaps are useful for documenting content architecture.
Spreadsheets are still a pretty darn useful format to use for capturing more detailed information about your site structure like URLs, tags, and internal linking. Make sure you consult with your developers on how to best format your spreadsheets so the data gets formatted correctly for their needs. Spreadsheets are also useful for documenting content architecture.
A flow diagram is another common type of sitewide architecture deliverable, often used in conjunction with a sitemap. Flow diagrams are useful for documenting system or product architecture.