First, just look at it. It's hard to describe in words. It's by a Seattle artist, John Grade, and it's on permanent display at a Seattle museum, MOHAI, which commissioned it for its new facility. (It's MOHAI day.)

It's made of the wood from the Wawona schooner, built in 1897 out of Douglas fir. It still smells a little, like fish and oil.

You walk inside the sculpture, which is hollow. This is the view inside it looking up. That's sky.

This is the view inside it looking down. That's Lake Union. The artist built the window in the floor and lit the sculpture as it stretches down into the water.

The sky part is more complicated than the lake part.

To actually cut through the historic building required all kinds of special pleading and permits, and the psychological effect is powerful: You disbelieve your eyes and sort of can't stop looking up toward the sky and down into the water as you're standing inside the sculpture.

When you look down, the water under your feet is dark. Grade wishes a beaver would swim by someday.

When you look up, what you see isn't actual sky. (It is not like Yoko Ono's 1966 Sky TV.) You could be forgiven for being fooled, because looking at the building from the outside, the sculpture juts up from the roof of the building. That's trickery. Grade couldn't get permission to cut through both floor and roof, so he had to pick. (He chose well.) Near the top of where the sculpture meets the ceiling, he cut out an area of hidden false roof. Inside it, he mounted a video projection of sky, and that's the surface you see when you look up.

What's playing is a recent loop of actual sky shot right there on site. But it can be swapped out for a movie of faraway sky, or better yet, sky from another time period.

They say the past is a foreign country, right? When you're inside the heart of the new history museum, the time period under your feet is always the present, but the time in the sky is mutable.