The waterfalls of the Columbia Gorge are the region's main tourist draw.  Multnomah Falls hosts around two and a half million visitors a year, making it Oregon's largest attraction.  But for second place, I'd give the nod to the balsamroot flower.  It grows in oak woodlands and open areas east of Cascade Locks, so numerous that it carpets the slopes of Dog Mountain and Rowena Crest in solid yellow beginning about mid-March and into early May.  In good years, hikers and sightseers fill parking lots on weekends to see the flowers announce the glory of spring.  Balsamroot doesn't have the daily regularity of a waterfall.  There is a short season of a few weeks and a peak that lasts perhaps a few days.  Some years, windy or cold conditions shred the blooms.  When that happens they are still lovely but unsuitable for a memorable photograph that tries to create an illusion of nature's perfection.  

Beyond mere beauty, balsamroot was good for physical sustenance.  The Journals of Lewis and Clark mention this plant as a food source for Indians: 

[Clark] Monday April 14th 1806 
I walked on Shore with Shabono on the N. Side through a handsom bottom.  met Several parties of women and boys in Serch of herbs & roots to Subsist on maney of them had parcels of the Stems of the Sun flower.  

Other notes indicate the stems were eaten unprepared.  The young plants are very nutritious, up to 30% protein.  They sustained people in the Gorge for thousands of years.  The seeds don't spread great distances, so it is curious how these flowers populated such a large area.  Since Indians collected the seeds to eat raw, grind into flour for cakes, or extract oil for cooking, they may have realized sowing the seeds would enhance the harvest.  It was patient work, as the plant takes at least eight years to flower from seed.  

In 2008 I started planting seed along with other volunteers to restore ancient fields that were lost to grazing.  In 2016 or 2017 the first flowers from these efforts will bloom.  I'll share a picture when that happens.