There are many...let me list it for you
In Delhi and NCR
1. Kutub Minar
2. Jama Masjid
3. Red Fort
4. Lotus Temple
5. Dilli Haat
6. Akshardham Temple
etc...
Within 300km of Delhi
1. Agra (for fort and Taj Mahal) 250km
2. Jaipur (for forts) 300 km
3. Haridwar (major pilgrimage) 270 km
4. Chandigarh 250 km
5. Bharatpur (Bird sanctuary) 210 km
Anything else mail me...
BoULevArd oF BrOKEn dReAmS
there is Nimrana fort i have heard its good place.