The four-door convertible based on a Regal GS you probably don't remember.

Name: Buick Cielo (pronounced see-A-low) meaning “sky” in Spanish

Debuted: 1999 North American International Auto Show in Detroit

Specs: Based on stretched and widened Regal GS platform, supercharged 3.8-litre V6 engine with 240 horsepower, four-speed automatic transmission, 20-inch wheels

Why We Remember It Now:

A four-door convertible is not something you see every day (we're excluding Jeeps obviously), especially one with an odd shape that started out in life as a traditional midsize saloon.

Today’s automotive scene is filled with just about every niche you can think of, including the crossover cabrio genre with the Range Rover Evoque Convertible and the forthcoming VW T-Roc Convertible. But what happened to the saloon convertible? It essentially died after the classic Lincoln Continental, with a couple of exceptions such as the 62 S Landaulet, the one-off LS600h Landaulet, and the stunning Cadillac Ciel.

1999 Buick Cielo concept

Before those three, Buick decided at the end of the 1990s to revive the saloon / cabrio oddity with this, the Cielo. The name might make you think of a mundane Daewoo saloon, but it actually makes more sense for this open-top concept since it means “sky” in Spanish. It started out in life as a Regal GS before losing its fixed metal roof to make room for three electrically retractable panels.

1999 Buick Cielo concept

The concept was engineered with a cable system incorporated within the roof’s rails to move those panels and the rear glass window back and forth. The roof folded into the trunk in a little over 30 seconds, effectively transforming the saloon into a five-seat, four-door convertible. With power-operated (via voice control) doors and a controversial shape, the Cielo was an unusual concept, to say the least.

1999 Buick Cielo concept

To make it happen, Buick’s engineers had to stretch the Regal’s wheelbase and widen the tracks while largely carrying over the saloon’s suspension. The concept sat on 20-inch wheels wrapped in bespoke Michelin tyres featuring the tri-shield logo embedded into the tread. Fancy.

Gallery: 1999 Buick Cielo concept

Interestingly, the one-off was seriously considered for series production and it was actually followed by a more conventionally styled Regal Cielo concept (see pictures at the end) a year later. That one too was labelled as a “potential limited-edition production model” by Buick, but it never happened.

Gallery: 2000 Buick Regal Cielo concept