Some 80 metres up from pitch level, the rider who leapt 160ft at last year's inaugural Supercross event was able to see right across the Welsh capital from one the highest vantage points in the country.
"It was a fantastic view from the Millennium Stadium roof, although it was a little bit scary looking down at the grass below," admitted Rennie. "Last year I jokingly asked if it might be possible to jump from one side of the roof to the other, so I guess this was the first step towards having a go at that.
"I was able to ride up and down the length of the roof and I even managed a few wheelies.
"The idea was to grab some attention ahead of next month's big event. If you thought riding on the roof was spectacular, just wait until the riders get back on the ground on 4 December and get going around the circuit."
The Millennium Stadium is on course to play host to the biggest crowd in British Supercross history when the fastest sport indoors returns to Cardiff.
A massive 20,000 race fans, the biggest ever in Britain for a Supercross event, saw the sport make its spectacular debut last year at what has become one of the most versatile sporting arenas in the country.
Supercross followed the likes of rugby union, rugby league, football, cricket and speedway into the closed roof stadium and made an impressive debut.
Britain's top stars will all be returning to the Millennium Stadium in December when home grown heroes Rennie and Neil Prince take on England's top riders in Paul Cooper and Carl Nunn.
Proud Welshman Prince will be defending his 250cc British Supercross title and England's Lewis Gregory is back to defend his 125cc crown.
Adding to the international flavour will be Australia's Kim Ashkenazi and Canadian rider Kyle Beaton. Ashkenazi was unable to contest the whole of last year's British championship but, after impressing in Cardiff last season, is back and determined to add the British title to his many Australian national championships.
"I couldn't do the whole series before but I want to win it this time," said Ashkenazi.
He will face stiffest competition from Cooper and Finnish rider Jussi Vehvilainen but Canadian Beaton is sure to figure high up the results.
Last year Cardiff also played host to an indoor demonstration of Supermoto, a cross between Supercross and road racing.
The experiment was such a success that promoters Future West have brought it back again this year. Future West are in talks with a number of leading Supermoto and road racers to take part in the Millennium Stadium event.
Following on from Rennie's world record indoor jump last year - he returns this year to increase the length of his jump by jumping diagonally across the stadium.
Future West spokesman John Hellam said; "Everything went very well for us at the Millennium Stadium last time and we are delighted to be back. We had a great crowd and hope to do the same again this time."
The Millennium Stadium hosts the third event in the Future West British Supercross Series following events in Sheffield and Glasgow. There will also be races in Dublin and Birmingham to round out Britain's premier indoor racing series.
Tickets are available from £10 for children and £18 for adults, or £44 for a family of four.
Call the Millennium Stadium Ticket Hotline (08705 582 582) to book tickets or call into the Millennium Stadium Ticket Office at 98, St Mary Street, Cardiff.
Tickets are also available online from ticketmaster. Click Here to purchase online.