The centre, with the troubled tower in the background

The �75m futuristic-looking complex opened in July 2001 on a derelict site beside the River Clyde in Govan.

Management describe the millionth visitor as "a milestone day" for the centre.

The 400ft tower, the only one in the world capable of revolving 360� from the ground up, shut for repairs in February 2002 and a spokeswoman would not commit to a date for its re-opening.

The tower, costing �10m, closed after it was found to have sunk because of damage to two bearings in the rotating base mechanism.

Wrangling over who was liable for the problem is understood to have delayed the repairs.

The hitch was the latest in a series of problems that have dogged the construction and operation of the tower.

BBC Scotland's new home is beside the centre

During its first year, the centre ran up losses of �1.25m and in November 2002, the shortfall was reported to be �0.75m.

However, efforts have been made to improve the marketing of the centre, which is located on Pacific Quay, where BBC Scotland's new headquarters will open in about three years time.

Director of development and marketing Fiona Colley said: "Our achievement today further confirms we are delivering extraordinary experiences.

"Recent successes include two world-class exhibitions - Life of Mammals and Mental, the current ground-breaking art/science installation which has attracted over 10,000 visitors in just three weeks.

"We were delighted to hear that three out of four visitors interviewed in a recent survey said they were at GSC because of a word of mouth recommendation or because they had enjoyed a previous visit so much."