A "pagan celebration" in the Old Royal High School and a large tree in Waverley Station are part of Edinburgh's art festival commissions this summer.

Works by leading contemporary artists Charles Avery, Marvin Gaye Chetwynd and Ariel Guzik, and the theme of The Improbable City, are part of the seven-strong slate of commissions for the Edinburgh Art Festival.

Avery has made a five-metre tall bronze tree, which will be placed within Waverley Station and, the festival say, it will "offer a point for meeting and reflection during the festival."

Performance artist Marvin Gaye Chetwynd has chosen the site of the debating chamber within the Old Royal High School on Calton Hill for her new commission, The King Must Die.

This "sumptuous and theatrical installation places the epic action from Mary Renault's novel The King Must Die within an operatic setting referencing the legendary Czech stage scenographer, Josef Svoboda" the festival says.

The Improbable City takes its name from Italo Calvino's Invisible Cities; a series of 55 short prose poems.

The festival, the biggest visual art festival in the UK, runs from July 30 to August 30.

Showing in the UK for the first time, South African artist Kemang Wa Lehulere will create a new large-scale wall drawing in chalk to be erased at the end of the festival.

French-Canadian artist Julie Favreau will present a new work, entitled She Century, in partnership with the Scottish National Gallery of Modern Art.

The festival will also see new commissions by Scottish and international artists Hanna Tuulikki and Emma Finn.

For The Improbable City, Hanna Tuulikki, an English-Finnish artist, composer and vocalist based in Edinburgh will present Sing Sign: A Close Duet, performances that exploit the architecture and acoustics of Edinburgh's historic 'closes'

Sorcha Carey, director of Edinburgh Art Festival, said: "The Improbable City' explores the work of artists who conjure alternative worlds in their work.

"Even without the fairytale topography of Edinburgh, a festival offers a natural home for the improbable - a moment when we are instinctively more open to discovery and experimentation.

"We are delighted to continue to expand the ambitions of our commissioning programme, with seven new projects by leading and emerging artists, including some of the very best practitioners from Scotland and several international artists showing in the UK for the very first time."

Four young artists have been chosen to work with the festival: Chilean postgraduate Antonia Bañados; Edinburgh-based Irish artist Ben Callaghan, Isle of North Uist draftsman Ross Hamilton Frew; and sculpture, performance and installation artist Jessica Ramm, currently based in Aberdeen.