Leffler Simes Architects | 2,272 followers on LinkedIn. Leffler Simes is well recognised as one of Australia's leading Architectural and Interior Design Practices | Leffler Simes Architects (LSA) continues to enjoy notable recognition as one of Australia's leading Architectural and Interior studios, with offices in Sydney and Melbourne. Its strong historical roots date back to the 1960's, having then been at the coalface of the dramatic expansion of the retail sector throughout Australia. This solid retail pedigree founded in the 1970's/ 80's, has been developed and enriched in more recent decades, earning our excellent reputation not only as a major retail Architectural and Interior Design practice, but making our mark on all architectural sectors.