Bay seniors interested in cultural activities but not museum mobs? Above Geyeserville the voluptuous 100 acre Oliver Ranch is studded with 18 site specific works by Andy Goldsworthy, Richard Serra and Bruce Nauman among others. The hitch is that only organized groups are allowed. 2-hour tours will be held only from April 15 to June 1 and September 15 to November 1 and visitors must donate a minimum amount to the sponsoring non-profit group. Tickets are generally $150 +. Well worth it.