Moravian loop through vineyards: Breclav - Lednice - Pavlov - Mikulov - Valtice - Breclav. 66 km, 680 m up (that's the sum; in fact there's one hill, 200 m up). Here you can see the route on a map: https://mapy.cz/s/1zXnu (just don't be discouraged by the Czech language - the map is really nice; you can see the elevation profile under 'zobrazit vyskovy profil trasy', right-hand panel; hint for the bold ones: you can install the mapy.cz maps on your smartphone). Suitable for both trekking and mountain bikes.
Cost: Einfach-Raus-Radticket for 5 people: € 54 (I hope it's valid for Breclav as well - I promis to check it), food and drinks in Czechia.
Remark: the route is very nice - so nice that some places (Mikulov, Valtice and Lednice with all their palaces and castles) can be crowded, especially if the weather is fine.