Kaunas Castle and Santaka Park
Start with the compact medieval landmark and the Nemunas/Neris confluence before the Old Town gets busier.
A proper Kaunas day with Old Town, Santaka, Vilniaus Street, Laisvės Alėja, and one bigger afternoon choice such as Pažaislis, Ninth Fort, Čiurlionis, or a modernism route.
Pick either Ninth Fort or Pažaislis for the afternoon; doing both makes the day less relaxed.
Start with the compact medieval landmark and the Nemunas/Neris confluence before the Old Town gets busier.
Walk the Old Town center, House of Perkūnas exterior, Cathedral Basilica area, Vilniaus Street, and the main pedestrian axis.
Keep lunch central so the afternoon choice does not start late.
Use this as the scenic architecture and nature version of the afternoon, with reservoir time if the weather is good.
Choose Ninth Fort for serious 20th-century history or Čiurlionis Museum plus a modernism walk for a culture-focused version.
Finish the sightseeing day with the easy city panorama before dinner.
Return to Laisvės Alėja, Old Town, or the riverside for dinner and a low-pressure second Kaunas evening.
A proper Kaunas day with Old Town, Santaka, Vilniaus Street, Laisvės Alėja, and one bigger afternoon choice such as Pažaislis, Ninth Fort, Čiurlionis, or a modernism route.