http://biz.yahoo.com/ap/060614/google_headquarters.html

Google Inc. is buying its Silicon Valley headquarters for $319 million in a deal covering the Internet search leader's nerve center – a cluster of buildings revered in high-tech circles as the "Googleplex."

if you're interested in more numbers and addresses, check this filing:
http://www.sec.gov/Archives/edgar/data/1288776/000119312506129861/d8k.htm