Pittsburgh's steep, rolling terrain invites adventurous design, but seldom gets it. That's the thinking behind a weeklong charrette meant to raise questions and stimulate discussion about how we build on our hills, in our valleys and along our riverfronts.

Five teams of architects and students have turned Carnegie Museum of Art's Hall of Sculpture into a design workshop this week, as they brainstorm hypothetical ideas for five open sites in Oakland.

Chance is a player in the process. The teams not only drew their sites from a hat, but also randomly picked the programs from two menus of potentially strange bedfellows: Each site must accommodate two coexisting but unrelated structures. The five teams are designing a movie theater and auto body shop (on the hillside behind the Frick Fine Arts Building down to Joncaire Street); a greenhouse and laundromat (on Dawson Street at South Bouquet); a basketball court and skateboard park (on Bates Street at Oakland Avenue); a car wash and motel (on Bates Street below Boulevard of the Allies) and a riverfront kindergarten and amphitheater (at Pittsburgh Technology Center).

On one menu of uses, the structures have predetermined sizes and limitations; on the other, decision-making about size and complexity of the structure is being left to the teams.

The charrette is a spinoff of the current Heinz Architectural Center exhibit, "Michael Maltzan: Alternate Ground," a 10-year retrospective of the Los Angeles architect's work, which continues through June 12. The exhibit's title reflects the way Maltzan's buildings can nestle into the ground or hover over it.

"So many buildings [here] seem to be unable to harness the possibilities of the hills and the rivers," said Heinz Architectural Center curator Raymund Ryan. "Why not apply the notion of alternate ground to Pittsburgh in a way that could be fun rather than staid?"

For each charrette team, the square footage it must allocate for the two structures is greater than that of the site.

"However they resolve programmatic needs, they will have to build up or down," Ryan said.

The exhibit's dozens of small process models, showing the evolution of designs, can stimulate thinking about solutions.

Maltzan and two architects from his office -- Steven Lee and Tim Williams -- are advisers to the charrette. Each team comprises a Pittsburgh architect, three area high school students and two architecture students from Carnegie Mellon University. In addition to Ryan, team leaders include architects Matthew Fineout, Kevin Gannon, Jennifer Lucchino and Spike Wolff.

From 3:30 to 5 p.m. tomorrow in the Hall of Sculpture, the charrette culminates with a public conversation about the designs. Participants include Laura Lee, chair of CMU's School of Architecture; Lisa Schroeder, director of the Riverlife Task Force; and Bob Reppe, zoning administrator for the city planning department. A reception will follow from 5 to 6 p.m., during which Ryan and Maltzan will sign copies of the exhibit catalog.