The National Botanic Garden of Wales will receive a further £1.35m of lottery funds, it has been announced.
Artist's impression of how John Belle's glasshouse will look
The garden said the money - which brings the total lottery grant to £22.5m - will be used to provide an "even better day out".
One of the new attractions will be a Tropical House designed by Welsh-born architect John Belle.
Mr Belle, who has transformed many of New York's most famous sites, unveiled his design at the garden on Monday.
Mike O'Connor, director of the Millennium Commission which donated the funds, said he was "proud" to be supporting the botanic garden.
"In a time when our natural environment is under greater threat than any time in human history we should all be proud that we have created the UK's first new national botanic garden for two centuries," he added.
Chairman of the garden's trustees Alan Hayward said the continued support of the commission underlined confidence in the garden's importance as a "national asset".
And Mr Hayward said attracting Mr Belle was a "fantastic coup" for the garden and Wales.
"This further enhances the garden's worldwide reputation as a millennium project of global significance," he said.
The architect's Tropical House will be in a corner of the Double-Walled Garden at the tourist attraction in Llanarthne, Carmarthenshire.
Mr Belle, who was born in Pontcanna, Cardiff, in 1932 said the project provided him with an opportunity to contribute to his homeland and he was "extremely honoured" to be working with the National Botanic Garden of Wales.
"It's a wonderful way for me to reconnect with my roots. This is a world-class institution, which is renewing the landscape."
Mr Belle's architectural projects in New York have included the city's own botanical garden, as well as the Chrysler Building, Grand Central Terminal, and the Rockefeller Centre.
New York's Rockefeller Centre is among the architect's projects
Three of his projects have won the Presidential Design Award, the US's highest award for public architecture and in 2003 he was made an honorary fellow of the Royal Society of Architects in Wales.
Mr Belle described the Wales' garden site as a "fabulous environmental project of world recognition".
In 2003, the 500-acre Welsh botanic garden was on the brink of closure after the decline in visitor numbers and rising debts.
The garden, which cost more than £40m to set up, was a project to mark the new millennium.
But visitor numbers slumped after it was opened by Prince Charles in 2000, and last year the garden needed a £1.3m rescue package to remain in business.
Culture minister Alun Pugh initially rejected calls for a £3m assembly bail-out, but a three-party rescue deal was eventually struck between the assembly government, Carmarthenshire Council and the Millennium Commission.