Broadway runs from US-101 straight down to the beach and the Promenade, and it is a classic American resort strip executed with conviction. Salt-water taffy shops, bumper cars, mini-golf, a bowling alley, ice cream parlors, and surf shops renting boards and wetsuits line both sides for several blocks. It is unashamedly commercial and cheerfully so — Seaside has been catering to Portland day-trippers for over a hundred years and has no identity crisis about it.
The stretch is worth walking even if you don't spend money. The old-fashioned arcade energy is genuine rather than nostalgic pastiche; some of these businesses have been in the same families for decades. The surf shops at the beach end are a good place to rent a wetsuit if you plan to get in the water. The bumper cars have been running since at least the 1970s.