After checking in at the Corinthia Budapest, stroll a short distance to the elegant Andrássy Avenue for coffee at a gluten-free friendly café, then join a guided walk through the UNESCO-lined boulevard to the grand façade of the Hungarian State Opera House where a quick interior tour highlights its gilded history. Continue to the nearby House of Terror Museum for a sobering, well-curated introduction to 20th-century Hungarian history before pausing for an early midday gluten-free lunch at Napfényes Restaurant (known for celiac-safe Hungarian dishes).
After a leisurely lunch, wander across the river to explore the hilltop charms of Buda Castle District, taking the funicular or a short taxi for easy access and panoramic views of the Danube and Parliament. Pause at the romantic Fisherman's Bastion for golden-hour photos, then descend to relax and soak the day away at the historic Gellért Thermal Bath, where thermal pools and art nouveau architecture offer a restorative, culturally rich spa experience before an early evening gluten-free dinner back near the Corinthia.
As daylight fades, take a short tram or taxi to explore the lively Váci Street area, then slip into the atmospheric Great Market Hall for a browse of local artisan goods and to pick up gluten-free snacks for later. Follow with a riverside stroll along the Danube Promenade toward the illuminated Elizabeth Bridge, pausing for night-time views of the glowing Hungarian Parliament Building; finish with a relaxed, late gluten-free dinner at Címke Bistro (noted for safe gluten-free options) before returning to the Corinthia to unwind.