Board a fast train from New Delhi / Hazrat Nizamuddin to Agra Cantt — Gatimaan takes ~1h40m and is the quickest option, leaving early morning for a full day in Agra.
World-famous 17th-century marble mausoleum; visit in the morning for softer light and fewer crowds. Note: Taj Mahal is open sunrise–sunset and is closed to general visitors on Fridays for prayers.
A UNESCO site and stronghold of Mughal emperors with great views of the Taj from its ramparts; open roughly sunrise–sunset so afternoon visits are fine.
Riverside garden across the Yamuna offers classic Taj views at sunset and is calmer than the Taj precinct; ideal late-afternoon stop (open sunrise–sunset).
Short road trip (~45–60 minutes) to the well-preserved Mughal ghost city of Fatehpur Sikri, built by Akbar and now a UNESCO site; best visited in the cooler morning hours.
Massive hilltop fort with ornate palaces, Sheesh Mahal and stunning views; fort opens around 8:00–8:30am and is best early to avoid heat and crowds. (Elephant rides available from the base but often limited; jeep/vehicle options available.)
City Palace showcases royal artifacts and courtyards (open ~9:30–17:00), and adjacent Jantar Mantar displays historic astronomical instruments (open ~9:00–16:30).
Spice Court offers classic Rajasthani and North Indian dishes; for a cultural experience consider Chokhi Dhani (an evening village-themed resort) — note Chokhi Dhani opens evenings around 6:00pm.
Explore Jaipur’s lively bazaars for jewelry, textiles, block-printed fabrics and handicrafts; stores typically open 10:00–20:00 so the afternoon is ideal.
If you want a memorable Rajasthani evening, Chokhi Dhani is an open-air village-themed experience with folk performances, traditional cuisine and activities; best to reserve in advance (opens ~6:00pm).
Take a fast afternoon/evening train back to Delhi — numerous Shatabdi and express options connect Jaipur and New Delhi in ~4–5 hours; book reserved seats in advance for comfort.